ö.js

ö.js - a small collection of useful stuff.

Usage:

(p)npm install ouml

import { random } from 'ouml'
let oneOrZero = random()

or, with treeshaking:

import * as ö from 'ouml'
let oneOrZero = ö.random()

Most methods are runnable within node/deno. Some methods require browser API:s, those are marked with [browser].

Modules

Includes modules chain, a method for chaining calls on any type, öbservable, a basic implementation of reactive values, övents, a collection of useful custom browser events, and colour, a simple way to work with oklch colours.

Import them from

import { chain, chainAsync } from 'ouml/chain'
import { observable, isObservable, observe } from 'ouml/öbservable'
import {
    resize,
    enterview,
    exitview,
    sticktotop,
    sticktobottom,
    swipe,
    clickoutside,
} from 'ouml/övents'
import colour, { Colour } from 'ouml/colour'

Methods

Generators / Iterators

Helper methods for iterations, less verbose than regular loops.

ö.range( start, end?, step? = 1 ) yields Number

Yields Numbers within specified range. Parameters end and step are optional. If end is not provided, range starts with 0, and ends with start. Handles negative values. Useful in for of loops, for example:

for (let i of ö.range(100)) doStuff(i)

ö.grid( width, height? ) yields { x, y }

Yields Object with x, y coordinates. If height is omitted, width is assumed. Use like so:

for (let i of ö.grid(8)) drawChessboard(i.x, i.y)

ö.times( times, f? = i => i, ...rest ) → Array

Calls a function times times, with index as argument. Additional arguments are passed on to f like so:

ö.times(100, (i, a, b) => i + a + b, 'a', 'b')

Returns an array containing the return values of f, or an array containing index values if f is undefined.

Array / Iterable

Methods for manipulating arrays or array-like objects. Inputs are coerced to Array, so String, Set and the like works as input as well. All methods are non-mutating.

ö.rangeArray( start, end?, step? = 1 ) → Array

Returns an Array populated with given range.

ö.map( iterable | obj, f | str ) → Iterable | obj.key

Same as a normal map, except it accepts a string as a shorthand for retrieving values from an object property, if given an iterable that contains objects. Oh, and it accepts all iterables, and returns String, Map, Set and TypedArray as appropriate. It's a map for Map! Edge case iterables such as NodeList get converted to an array.

Oh, and it's a map for Objects! In the rare case that you would mant to map over the own properties of an object, that also works.

ö.map({ a: 1, b: 2 }, ([k, v]) => [k, v + 1]) // returns { a: 2, b: 3 }

Mapping functions for Maps and Objects receive an array in the form of [key, val] as a value argument, and must return an array in the same format.

ö.unique( arr ) → Array

Returns an Array with unique entries.

ö.shuffle( arr ) → Array

Returns a new shuffled Array.

ö.sample( arr, samples? = 1 ) → Array item | Array

Returns random sample from arr, or an array of samples if samples is larger than one.

ö.sum( arr ) → Number

Sums arr, with Number coercion.

ö.mean( arr ) → Number

Calculates mean value of arr, with Number coercion.

ö.product( arr ) → Number

Returns product of arr, with Number coercion. Reaches Number.MAX_VALUE rather quickly for large arrays, so use with some caution.

ö.geometricMean( arr ) → Number

Calculates the geometric mean of arr, with Number coercion. May return Infinity for large arrays or large numbers, since it uses ö.product.

ö.median( arr ) → Number

Calculates median value of arr, with Number coercion.

ö.max( arr ) → Number

Returns largest value in arr.

ö.min( arr ) → Number

Returns smallest value in arr.

ö.groupBy( arr, prop | f, asObject? = false) → Map | Object

Returns a Map with keys corresponding to prop values, holding grouped values as arrays. Optionally returns an object if asObject is set to true.

If prop is a string, takes an iterable of objects with a common property. If prop is a function, takes a function returning keys for grouping based on arr contents. The function receives value, index, array as arguments.

Tree structures

ö.mapToTree( arr, idProp | f, parentProp?) → Nested array

Maps a flat array of objects to a tree structure. Objects with children get a new children property, unsurprisingly containing an array of children 🙄. Leaf nodes have no children property. Works in one of two ways:

Either you provide an idProp and a parentProp, where the ìdProp holds a value unique to every item in the array, and parentProp holds a reference to the parent's idProp value (useful for example if you get a flattened hierarchic list from an api).

Or, you provide a mapping function responsible for providing a unique key for the item, and a unique key for the parent. The function receives value, index, array as arguments, and should produce an array with [ ownKey, parentKey ]. If the item has no parent, set parentKey to null. Useful for example for mapping urls to a hierarchy.

Parentless children (orphans) will be discarded.

Example:

let flat = [
    { id: '1' },
    { id: '1.1', parent: '1' },
    { id: '1.1.1', parent: '1.1' },
    { id: '2' },
    { id: '2.2', parent: '2' },
]

let tree = ö.mapToTree(flat, 'id', 'parent')
// or
let sameTree = ö.mapToTree(flat, item => [
    item.id,
    item.id.split('.').slice(0, -1).join('.'),
])

ö.reduceDeep( arr, f, subArrayProp, initial? ) → value

Reduces arrays of nested objects to a single value. subArrayProp is a string matching the property containing nested arrays.

The reducer function f receives accumulator, value, index, array as arguments. initial can be omitted, just like the native reduce, in that case the first item of arr is used as the initial value.

Example:

let arr = [
    {
        value: 1,
        children: [
            { value: 1 },
            { value: 1 },
            { value: 1, children: [{ value: -4 }] },
        ],
    },
]

ö.reduceDeep(arr, (acc, v) => acc + v.value, 'children', 0) // returns 0

ö.mapDeep( arr, f | prop, subArrayProp, flatten? = false ) → Array

Maps over arrays of nested objects. subArrayProp is a string matching the property containing nested arrays.

If f is a function, its return value is mapped to a new array. The function receives value, index, array as arguments. If f returns an object, and flatten is false, the structure of the original arr is preserved, and a property matching subArrayProp is added to the object, containing its children.

If f is a string, the value of the property matching f is returned, in a flattened array.

ö.filterDeep( arr, f | value, subArrayProp, prop? ) → Array

Finds items that match f in arrays of nested objects. subArrayProp is a string matching the property containing nested arrays.

If f is a function, returns items where f returns true. The function receives value, index, array as arguments. If f is a function, prop can be omitted.

If f is not a function, the value of f is compared to the value of property prop.

Returns a flat array with matching items, regardless of depth.

ö.findDeep( arr, f | value, subArrayProp, prop? ) → Array item

Same as ö.filterDeep, except it returns first match.

Set operations

Methods for comparing arrays or array-like objects. Inputs are coerced to Set. All methods return a new Array, or Boolean. The outputs adhere to strict set logic. If the inputs are Arrays, duplicate items are removed. All these methods are wrappers around internal Set methods, but returns arrays. (Available in evergreens and in node 22+)

ö.intersect( a, b ) → Array

Intersection, returns elements that are members of both a and b. Example:

ö.intersect([0, 1], [1, 2]) // returns [1]

ö.subtract( a, b ) → Array

Difference, returns members of a but not members of b, i.e. subtracts b from a. Example:

ö.subtract([0, 1], [1, 2]) // returns [0]

ö.exclude( a, b ) → Array

Symmetric difference, returns elements that are members of a or b, but not both. Example:

ö.exclude([0, 1], [1, 2]) // returns [0, 2]

ö.union( a, b ) → Array

Returns (unique) members of both a and b. Example:

ö.union([0, 1], [1, 2]) // returns [0, 1, 2]

ö.isSubset( a, b ) → Boolean

Returns true if a is a subset of b.

ö.isSuperset( a, b ) → Boolean

Returns true if a is a superset of b.

ö.isDisjoint( a, b ) → Boolean

Returns true if a and b share no members.

Logical / generic / functional

ö.isEqual/ö.equals( a, b, deep? = true ) → Boolean

Checks equality by value rather than reference. Compares prototypes, and uses Reflect.ownKeys to compare all own keys, including symbols. Works for all basic types and most built in classes, but may produce unexpected results in edge cases. Equality is tricky, and depends on what you personally beleive to be equal 😇. Does deep comparison by default, and may be slow for large data structures. If deep == false, does flat comparison instead.

ö.clone( v, deep? = true, immutable? = false ) → cloned value

Performs cloning of most common types, including Array and typed arrays, Map, Set, Date and objects. Defaults to deep cloning, set deep to false for shallow cloning. Tries to preserve prototype when cloning objects, but may fail in untested edge cases. Set preservePrototype to false to disable this (this is somewhat faster). Does not clone functions, and doesn't handle circular references. Use with some caution 🤫.

The native structuredClone is probably slower (by alot!) in most cases, errors on functions, and doesn't preserve prototype, but it handles circular references. Choose wisely!

ö.immutable( v, deep? = true ) → immutable value

Returns a freezed clone of v. Set deep to false to make only top level immutable.

ö.id( v ) → v

Identity, takes and returns v.

ö.pipe( v, ...funcs ) → value

Pipes function calls for a value. For multiple arguments, use closures. Usage:

ö.pipe(
    1,
    x => x * 6,
    x => x ** 2,
    x => x + 6,
    ö.log,
) // logs 42

ö.toPiped( ...funcs ) → function( v ) → value

Pipes function calls, and returns a function that takes the value to pipe. The data last save for later version of pipe. Usage:

const myPipe = ö.toPiped(
    x => x * 6,
    x => x ** 2,
    x => x + 6,
    ö.log,
)
myPipe(1) // logs 42

ö.pipeAsync( v, ...funcs ) → Promise

Same as ö.pipe, but awaits functions and returns a Promise.

ö.toPipedAsync( ...funcs ) → function( v ) → Promise

Pipes function calls, and returns a function that takes the value to pipe. That function returns a Promise.

ö.curry( f ) → function

Returns a curried version of f, allowing partial application of arguments. If f takes three arguments, it can be called like so:

const f = (a, b, c) => a + b + c
const curried = ö.curry(f)

curried(1)(2)(3) // returns 6
// or
const partial = curried(1, 2)
partial(3) // also 6

ö.memoise/ö.memoize( f, keymaker? ) → f

Creates and returns memoised functions. By default, the arguments to the memoised function are used as key for storing the result (If only one argument, the raw input is used as key, if more than one, the arguments are joined to a string). If the arguments are objects instead of primitive values, you should provide a keymaker. keymaker receives all inputs from the memoised function, and should return something unique to use as a Map key for a given set of inputs. Use for example JSON.stringify when you expect objects as input.

ö.createEnum( object ) → Object

Creates and returns an enumerable, i.e. a frozen object where the keys have unique values. Lets you create kinda sorta vanilla typechecking light, but at runtime 🤪. Takes an object, or strings, or an array of strings, as input. In order for codehinting to work, you need to provide an explicit object. Example:

const SIZES = ö.createEnum('small', 'medium', 'large')
// or:
const SIZES = ö.createEnum(['small', 'medium', 'large'])
// or:
const SIZES = ö.createEnum({
    small: Symbol('small'),
    medium: Symbol('medium'),
    large: Symbol('large'),
})
giveMeIcecream(SIZES.large)

ö.data( obj, key?, value? ) → data | data.key

Associates obj (Can be an Object or a Symbol) with data via a WeakMap. With only key set, acts as a getter for key. With key and value set, acts as a setter. Useful for associating data with DOM elements. If given an Element, it parses the dataset property and adds its properties to data.

If no key, returns data object.

Mathy

ö.random( min, max, float? = false ) → integer | Number

Shorthand for random integers between min and max-1. If max is omitted or Boolean, assumes a min value of 0. If max is Boolean, float is assumed. If float is true, returns float instead of integer.

ö.randomNormal( mean? = 0, sigma? = 1 ) → Number

Returns random number from reasonably approximated normal distribution, centered around mean, with more or less 68.2% of the sample set within ± sigma. Values max out at a bit above ± 3 sigma, with extreme outliers up to about ± 4 sigma. There are more mathematically accurate methods to do this, but this method is fast, and good enough for most people. Use it for fun and visuals, not for statistical analysis 🤓.

ö.round( n, precision? = 0 ) → Number

Returns n rounded to precision decimals.

ö.clamp( n, min, max ) → Number

Clamps n between min and max.

ö.between( n, min, max ) → Boolean

Checks if n is between min and up to, but not including, max.

ö.normalise/ö.normalize( n, min, max, clamp? = true ) → Number

Normalises n to a value between 0 and 1, within range given by min and max. If clamp == true and value of n is out of range, the value is clamped.

ö.lerp( a, b, t ) → Number

Interpolates linearly between a and b. t is a percentage value between 0 and 1.

ö.smoothstep( a, b, t ) → Number

Interpolates smoothly between a and b. t is a percentage value between 0 and 1.

ö.easeIn( a, b, t ) → Number

Eases in from a to b. t is a percentage value between 0 and 1.

ö.easeOut( a, b, t ) → Number

Eases out from a to b. t is a percentage value between 0 and 1.

ö.nthRoot( x, n ) → Number

Returns nth root of positive number, for example

ö.nthRoot(256, 8) === 2

ö.factorial( n ) → Number

Returns the factorial of n.

ö.nChooseK( n, k ) → Number

Returns the number of ways to choose k elements from a set of n elements, i.e. the binomial coefficient.

ö.toPolar(x, y) → { r, theta }

Converts cartesian coordinates to polar.

ö.toCartesian(r, theta) → { x, y }

Converts polar coordinates to cartesian.

String

ö.prettyNumber( n, locale? = 'sv-SE', precision? = 2 ) → String

Returns n rounded to precision decimals and formatted by n.toLocaleString(). Defaults to swedish formatting, because why not! locale is optional, if second argument is Number, precision is set instead.

ö.wrapFirstWords( s, numWords? = 3, startWrap? = '<span>', endWrap? = '</span>', startAtChar? = 0 ) → String

Returns s with first numWords words wrapped in startWrap and endWrap. Matches first words up to and including first punctuation. Optionally starts matching at index startAtChar. Matches special chars for nordic languages as well as ', ’ and -.

ö.toCamelCase( str ) → String

Returns regular sentence, kebab-case or snake_case string converted to camelCase. Leaves --custom-properties alone.

ö.capitalise/ö.capitalize( str ) → String

Capitalises first letter. No fuss!

ö.toKebabCase( str ) → String

Returns regular sentence or camelCase string converted to kebab-case. Leaves --customProperties alone.

ö.randomChars( numChars? = 10 ) → String

Returns numChars random characters. Max for numChars is 100. Useful for producing unique values (Or, to be precise, with a 1/426 825 223 812 027 400 796 974 891 518 773 732 340 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 chance of being a dupe 🤯).

ö.stripTags( str ) → String

Returns a string without html tags.

ö.when( bool, whenTrue, whenFalse? ) → value | empty string;

A slightly more readable wrapper around a ternary expression. Returns whenTrue if bool is true, otherwise returns the empty string. Optionally returns whenFalse if specified. Useful primarily in template strings.

Async

Awaitable wrappers for setTimeout, requestAnimationFrame and events. Takes an optional awaited f with no arguments. If f is provided, returns result from f, otherwise returns undefined. (Except for ö.waitFrames, which calls f every frame if everyFrame is true, but only returns the result of the final call.)

ö.wait( t? = 0, f?, resetPrevCall? = false ) → Promise

Waits t milliseconds. If resetPrevCall == true, previous pending call is rejected.

ö.nextFrame( f? ) → Promise

[browser] Waits one frame.

ö.waitFrames( n? = 1, f?, everyFrame? = false ) → Promise

[browser] Waits n frames. If everyFrame == true, callback is executed every frame.

ö.waitFor( selector, event, f? ) → Promise

[browser] Waits for specified event. Takes only one element, and one event type.

ö.load( url, isJSON? = true, errorMessage? = null, settings? = {} ) → Promise

[browser (Alternatively: Use node 18+)] Loads (and parses) JSON. Optionally loads HTML. Super simple fetch wrapper. On error, simply returns the error message, or optionally returns your custom error message. If you need to pass headers or other settings to the fetch call, use the settings object.

ö.pipeAsync( v, ...funcs ) → Promise

See ö.pipe.

Throttling

ö.throttle( f, t? = 50 ) → Function

Throttles execution of f to one call per t milliseconds. If called multiple times per period, the last call gets executed.

ö.debounce( f, t? = 50, immediately? = false ) → Function

Debounces execution of f until no calls are made within t milliseconds. If called multiple times per period, the last call gets executed. If immediately is set to true, the first call gets executed as well.

ö.onAnimationFrame( f ) → Function

[browser] Defers execution of f to next animation frame. If called multiple times per frame, the last call gets executed.

Error handling and logging

All logging methods can be silenced globally by calling ö.verbose(false).

ö.attempt( f, handler?, ...args) → result | handled error

Wrapper around a try statement. It attempts to call f with ...args, and returns the result. If f throws, it returns handler, or the return value of handler if handler is a function. handler gets the error as argument. handler defaults to a function returning the caught error.

let tried = ö.attempt(tryThis, 'It failed', 1, 2, 3)
// or
let tried = ö.attempt(() => tryThis(1, 2, 3), 'It failed')
// or
let tried = ö.attempt(tryThis, e => ö.log(e.message), 1, 2, 3)

ö.attemptAsync( f, handler?, ...args) → result | handled error

Same, but awaits f and handler.

ö.verbose( isVerbose?, isThrowing? ) → { isVerbose, isThrowing }

Set isVerbose, turns off error/message logging when set to false. Defaults to true. Optionally set isThrowing to true, in order to throw errors instead of logging them.

Returns an object containing the current state of { isThrowing, isVerbose }.

ö.error( error, ...rest ) → console.error or thrown Error, arguments

Logs errors to console, optionally throws instead. Returns single argument, or multiple arguments as an array.

ö.warn( message, ...rest ) → console.warn, arguments

Outputs arguments to console. Returns single argument, or multiple arguments as an array.

ö.log( ...messages ) → console.log, arguments

Outputs arguments to console. Returns single argument, or multiple arguments as an array. Can be used like so: let x = ö.log( y*z ); or to tap into a call chain.

ö.time( f?, label? ) → logs time, f return value | undefined

The basic usecase is as a simple wrapper for console.time, optionally with a label. If fis a string, it is used as a label. In that case, the timer ends when calling ö.timeEnd with a matching label.

Optionally, it accepts a function with no arguments, which gets timed, called and its value returned. In this case console.timeEnd is called internally.

ö.timeEnd( label? ) → logs time

Simple wrapper for console.timeEnd.

ö.message( str ) → 'ö says: ${str}'

Wrapper for internal messages.

Basic type checking

Less verbose than typeof/Array.isArray/instanceof:

ö.isBool( v ) → Boolean

ö.isNum( v ) → Boolean

ö.isInt( v ) → Boolean

ö.isBigInt( v ) → Boolean

ö.isStr( v ) → Boolean

ö.isSym( v ) → Boolean

ö.isFunc( v ) → Boolean

ö.isArr( v ) → Boolean

ö.isNull( v ) → Boolean

ö.isDate( v ) → Boolean

ö.isMap( v ) → Boolean

ö.isSet( v ) → Boolean

ö.isRegex( v ) → Boolean

ö.isError( v ) → Boolean

ö.is( v ) / ö.isDefined( v ) → Boolean

ö.isnt( v ) / ö.isUndefined( v ) → Boolean

ö.isObj( v ) → Boolean

ö.isObj excludes Array, Map, Set, Date and RegExp. And null, of course.

ö.isPlainObj( v ) → Boolean

Checks if v is a plain object a.k.a. pojo, that is, has the same prototype as Object.

ö.isNakedObj( v ) → Boolean

Checks if v is a naked object, that is, has null as prototype.

ö.isIterable( v ) → Boolean

Checks for [Symbol.iterator] in v.

Type conversion

ö.mapToObj( map ) → Object

Any iterable except strings work, but produce arraylike objects without a length.

ö.objToMap( obj ) → Map

DOM and browser

ö.getLocal( item ) → Object

[browser] Gets item from local storage, if any. Converts item to Object via JSON.parse.

ö.setLocal( item, v ) → v

[browser] Sets item in local storage to v, and returns v.

ö.getCss( prop, selector? = ':root') → css property value

[browser] Gets prop on selected element, or from document.documentElement if selector is unset, and returns v. Mainly used for getting global --props, using css as master for global variables.

ö.setCss( prop, v, selector? = ':root') → v

[browser] Sets prop to v, optionally on selected element, and returns v.

ö.createElement( html, isSvg? = false ) → Element

[browser] Creates an Element from an html string. Optionally creates an SVGElement.

ö.parseDOMStringMap( o ) → Object

Parses a DOMStringMap as JSON. Used internally when reading from Element.dataset.

ö.deepest( element, selector? = '*' ) → Element

[browser] Finds deepest Element in element, optionally matching selector.

Random stuff

ö.rorövovarorsospoproråkoketot( str ) → String

Converts string to Rövarspråket.

Chain

Chain a.k.a TypelessScript lets you chain any method calls, on any type, kind of like a pipe on speed 🧙, or a jQuery for any object. It simply shoves the return value around, allowing you to think about more important stuff than intermediate variables.

Here's an example:

import { chain } from 'ouml/chain'

let guessWhat = chain(11)
    .f(v => [...Array(v).keys()])
    .map(v => v ** v)
    .sum()
    .toString()
    .length()
    .return()

It takes the number 11, makes an array of integers using the .f() directive, maps the values to the power of themselves, sums them using an ö method, converts the resulting number to a string, gets the length of the string, and returns it.

Here's another:

import { chainAsync } from 'ouml/chain'

let errorMessage = 'error'

let nameOfPriciestProduct = await chainAsync('https://dummyjson.com/products')
    .load(true, errorMessage)
    .returnIf(v => v === errorMessage)
    .products()
    .sort((a, b) => a.price > b.price)
    .at(0)
    .title()
    .return()

It takes a url, loads it as json using an ö method, handles the error case, gets the products property of the json object, sorts it, gets the first one, gets the title, and returns it. Simple as that!

Usage

chain chains method calls, but with some quirks and gotchas. For example, properties on objects can be retrieved by calling the property name as a function. Methods on objects in the global scope can be accessed by an underscore, for example Object_groupBy(). Also, if a method in the chain creates an error, the step is skipped by default (and the error is logged), prioritising a return value. You can override this by setting isThrowing to true, or handle the error with a .try(). Use like so:

import { chain, chainAsync } from 'ouml/chain'

let processedValue = chain('AnyValueOfAnyType')
    .anyMethodOnCurrentType()
    .anyPropertyOnCurrentValue()
    .anyMethodInÖ()
    .anyMethodInGlobalScope()
    .AnyObjectInGlobalScope_anyMethod()
    .f(anyFunction)
    .peek() // Logs current value and type
    .returnIf(anyFunctionReturningABoolean)
    .try(tryFunction, catchFunction)
    .return()

Or like so, saving the chain for later, providing the value last:

import { chain } from 'ouml/chain'

const doStuffAndThings = chain().f(coolStuff).f(wonderfulThings).end()

let processedValue = doStuffAndThings('anyValue')

A quick note on performance: chain does string matching, proxying and other fun stuff that adds some overhead. It adds a small hit performance-wise, and might not be the best option in a game loop 😇. It's mainly a proof of concept, but since it produces some really nice, terse and readable code, it might come in handy in some situations!

Methods

Chain exports two methods:

chain( value?, isThrowing? = false, isAsync? = false ) → Proxy

Chain wraps a value, and creates a Proxy that handles the chaining. chain evaluates lazily, so nothing is calculated until .return() or .value is called. Errors are skipped by default, set isThrowing to true to throw errors instead. Optionally, set isAsync to true to handle async values, or use:

chainAsync( value, isThrowing? = false ) → Proxy

Same as chain, but results in a Promise.

"Methods"

The chain proxy defines a few special cases, that look and behave like methods:

.return() → value

Executes call chain, and returns computed value.

.value → value

Same as .return(), executes call chain, and returns computed value.

() → value

A method call with no arguments has the same effect as .return() or .value, executes call chain, and returns computed value.

.end() → function( value ) → value

Ends the chain, and returns a function that takes a value and executes the chain on it, allowing you to save a chain as a function.

.returnIf( function ) → value | Proxy

Guard clause, lets you exit the call chain early. The function receives the current value as argument, and is expected to return a boolean. Returns current value on truthy values, otherwise continues call chain.

.try( tryFunction, catchFunction? ) → Proxy

Error handler, lets you try a function, and run catchFunction if it throws. tryFunction receives the current value as argument, catchFunction receives value, error as arguments. catchFunction defaults to v => v, simply passing the previous value along.

.peek() → Proxy

Lets you peek into the call chain, logging current value and type to the console.

.f( function ) → Proxy

f allows arbitrary functions to be passed into the call chain. The function receives the current value as argument. f is particularly useful for methods defined in a function or module scope, since these scopes are unreachable otherwise.

( function ) → Proxy

A variant for passing in arbitrary functions is directly with parentheses, in effect calling the proxy as a function, with your function as the argument. This in turn can be chained, like so:

let v = chain('Hi')(letsDo)(cool)(stuff)()

This doesn't play that nicely with Prettier, if you happen to use that, but it's cool!

.anyMethodOnCurrentType( ...args? ) → Proxy

Lets you call a method of the current value. Methods are called "as is", so for exemple a .map(v => v) on an array takes a function, .toUpperCase() on a string takes no argument, and .toUpperCase() on a number is skipped along with a warning to the console, since no such method exists on a number.

.anyPropertyOnCurrentValue( newVal? ) → Proxy

Lets you access properties on the current value as a method call, for example .length() to get the length of a string or an array. If newVal is provided, sets the property to newVal, and passes newVal along the chain.

.anyMethodInÖ( ...args? ) → Proxy

Lets you pass any ö method into the chain. The current value is passed as the first argument, so if you would normally call ö.sum(arr), in a chain you need only call .sum().

.anyMethodInGlobalScope( ...args? ) → Proxy

Lets you pass any global method into the chain. The current value is passed as the first argument, so if you would normally call fetch('http://some.url'), in a chain you need only call .fetch().

.anyObjectInGlobalScope_anyMethod( ...args? ) → Proxy

Lets you pass any method on a global object into the chain. The current value is passed as the first argument, so if you would normally call JSON.parse(someString) or Array.from(someIterable), in a chain you need only call .JSON_parse() or .Array_from().

If you have defined any methods in the global scope that have underscores in their names, use .f(v => my_global_method(v)) instead, since underscores get parsed out by the proxy.

Öbservable

öbservable is loosely based on how vue.js handles reactivity, but it is much simpler, and, truthfully, not as good 🤪. It is, however, shockingly small, 1Kb minified.

Usage

öbservable uses Proxy to intercept changes to observable values, and in doing so detects for exemple direct array manipulation. Use like so:

import { observable, isObservable, observe } from 'ouml/öbservable'

let obs = observable(['a', 'b', 'c'])
let lengthObserver = observe(
    () => obs.length,
    v => ö.log(`The length is ${v}`),
)
let firstItemObserver = observe(
    () => obs[0],
    v => ö.log(`The first item is ${v}`),
)
// Logs The length is 3, The first item is a

await ö.wait(666)
obs.shift()
// Logs The length is 2, The first item is b, after 666ms

You can also use the raw observable as input to observe, or call observe directly on the observable (due to some Proxy trickery):

let thisGuy = observable({ name: 'Guy', surname: 'This' })

observe(thisGuy, (val, oldVal, changedProp) =>
    ö.log(`${changedProp} has changed`),
)

thisGuy.observe(v => ö.log(`Name: ${v.name}  Surname: ${v.surname}`))

thisGuy.surname = 'Fawkes'

When called as a method, the getter argument to observe is omitted.

Methods

öbservable exports three methods:

observable( value ) → observable object

Takes a value, and returns it wrapped in an observable Proxy, recursively wrapping nested objects as well. If you add a new property to an observable, the value of the new property is made observable as well (if it's not a primitive).

If value is a primitive (String, Number, Boolean etc), the value is wrapped in an object with a single property: value. You cannot assign to a primitive observable value directly, you need to use the value prop instead, or else you'd overwite the proxy.

let x = observable('foo')
observe(x, ö.log)
x = 'bar' // Won't work.

let x = observable('foo')
observe(x, ö.log)
x.value = 'bar' // Assign to value instead.

observe( getter, callback ) → observer object

Takes a getter, responsible for reading an observable and producing a value, and a callback that acts on the value. The getter can be either a raw observable, or a function returning the processed value of an observable. The callback receives value, prevValue, updatedKey and observer as arguments. The values passed to callback are copied from the observable, so you can't mutate the observable value in the callback (that would create an infinite loop anyways, so don't try it 🤯).

If you're observing an object, updatedKey can be useful in order to retrieve and act on only the property that changed. However, if you're destructuring multiple properties from a nested object, updatedKey refers to the key local to the updated object, so in this case make sure not to use the same property name on different levels . observer is a reference to the observer object, giving access to primarily the stop() method.

If the getter is a raw primitive observable, the value is unwrapped before the callback is called, like so:

let o = observable(0)
observe(o, v => ö.log(`The value is ${v}`)) // logs 'The value is 0'

or

let o = observable(0)
o.observe(v => ö.log(`The value is ${v}`)) // logs 'The value is 0'

If the getter is a function, you need to access the value prop, like so:

let o = observable(0)
observe(() => `The value is ${o.value}`, ö.log) // logs 'The value is 0'

It's a matter of taste, really.

When working with deep data structures, you can observe an entire object structure, and receive updates when properties on child objects change, like so:

let deep = observable({
    a: { b: { c: { d: "What's the purpose of it all?" } } },
})
observe(deep, ö.log)
deep.a.b.c.d = 'Deep stuff'

The drawback with this, however, is that the entire object returned from the getter gets deep cloned every time the observer is triggered (to avoid recursion among other things). This is fairly untested with regards to performance, so try to keep the data structure fairly small. There are possible optimisations to be done here, maybe in the future...

When working with larger data structures, try to be as specific as possible in the getter. As a rule of thumb, get the values you output in the callback, nothing more. Maybe something like this:

let bigAssObservable = observable(bigAssObject)
observe(() => {
    let {
        stuff,
        that,
        we,
        childObject: { really, need },
    } = bigAssObservable
    return { stuff, that, we, really, need }
}, renderSmallPartOfBigAssObject)

isObservable( value ) → Boolean

Checks whether a value is observable or not, just in case you'd forgotten.

Observable object

observable() returns observables, responsible for notifying observers when their value changes. When an observable is read by an observer, the observer is added to an internal Set of observers. These get updated when values change. If the observable holds a primitive value, it has a value property, otherwise values are accessed just like a regular object or array. The observable also holds Symbols for observable and primitive, used internally, and for easier debugging.

You can also call observe directly on an observable object (observe is not a proper property on the object though, this is handled by the getter in the Proxy).

Observer object

observe() returns observers, holding the current value of the observed observable, and a few methods and properties for flow control. You don't need to save a reference to the object, but it might come in handy if you want to stop observing later on.

let x = observable(0)
let o = observe(x, ö.log)
x.value = 666 // logs 666
o.stop()

o.pause()

Pauses the observer.

o.unpause()

You'll never guess.

o.stop()

Stops the observer from receiving updates, and unsubscribes the observer from observables.

o.update()

Updates current value and calls callback if the value has changed. Called internally by the observable.

o.value

Holds the most currently returned value from the getter. Usable mostly for debugging.

o.prevValue

Holds the previous value. Usable mostly for debugging.

o.paused

Set to true if paused, otherwise undefined.

o.stopped

Set to true if stopped, otherwise undefined.

Övents

övents is a collection of should've-been-in-the-browser-already custom events.

Usage

Övents implements the svelte/action interface, and are usable as svelte actions, but can be used in any browser context like so:

let el = document.querySelector('#someElement')

resize(el)
// or, if you need cleanup:
let resizer = resize(el)

el.addEventListener('resize', someCallback)

// When you're done:
resizer.destroy()

Events

resize

Emit when an Element gets resized, as observed by ResizeObserver. Relays the ResizeObserverEntry in the details object.

enterview, exitview

Emit when an Element's bounding box enters or exits the viewport.

sticktotop, sticktobottom

Emit when an Element's bounding box touches the top/bottom of the viewport. Useful for detecting when an Element with position: sticky sticks to the viewport. One caveat: This works only if the sticky elements have top: 0 or bottom: 0. Event status is passed via a sticky prop on the details object.

swipe

Emits swipeleft, swiperight, swipeup, swipedown when user swipes on a touch device.

clickoutside

Emits on click or tap outside Element.

Colour

Oklch lets you use colour in an understandable way. oklch is great! Use oklch!

Hsla used to be great, but ever since Css colour level 4 became the norm, there have been much better options for working with colour, so ö.hsla and ö.toHsla have been removed as of version 0.3.0.

And since oklch and its sibling oklab are great, there's really no need to support any other colour space for day-to-day use.

The colour module provides simple functions for working with immutable oklch colours in js. It exports the default function colour(), that creates Colour objects. It also exports isColour().

Use like so:

import colour, { isColour } from 'ouml/colour'

let red = colour('#f00')
let blue = colour('hsl(239.96 100% 50%)')
let purple = red.mix(blue)

ö.log(`${purple}`)
// logs oklch(53.9985% 0.1337 316.0189 / 1)

ö.log(isColour(purple), isColour(purple.valueOf()))
// logs true, false

Or without intermediaries:

ö.log(`${colour('#f00').mix('hsl(239.96 100% 50%)')}`)
// logs oklch(53.9985% 0.1337 316.0189 / 1)

Or have a look at a small demo.

colour()

colour( lightness | cssString | Colour, chroma, hue, alpha ) → Colour

The colour function creates Colours from either css strings in hex/rgb/rgba/hsl/hsla/oklch format, or a Colour, or numeric values for the colour channels.

Inputs are clamped to valid values. lightness takes values between 0 and 1, chroma takes values between 0 and 0.4, hue takes values between 0 and 360, and alpha takes values between 0 and 1.

Colour methods

The methods that return Colour are chainable, and the methods that return an array of Colours are chainable via .map().

All methods that interpolate between colours, such as .mix() or .palette(), interpolate through oklab by default, since oklab is more true to saturation when interpolating. If you want a poppier feel, go for oklch instead. Oklch and oklab are the only colourspaces supported. Try out interpolation through different colour spaces here to see why.

Colour.lightness( v? ) → Colour

Getter/setter for the lightness value. Gets the value when used without argument. Sets the value if number is provided, or sets the value by calling v if a function is provided. The function gets the current lightness value as argument.

Colour.chroma( v? ) → Colour

Getter/setter for the chroma value. Works the same as .lightness(). For example, a saturate method might look like this:

const saturate = (clr, amount = 0.01) => clr.chroma(v => v + amount)

Colour.hue( v? ) → Colour

Getter/setter for the hue value.

Colour.alpha( v? ) → Colour

Getter/setter for the alpha value.

...Colour

Colour objects spread nicely into arrays, in [l, c, h, a] order.

Colour.valueOf() → { lightness, chroma, hue, alpha }

Returns an object with values. Useful for console.log or to get all values out.

Colour.toString() → css string

Returns a css string. Useful for all sorts of colour related things. Called implicitly on string concatenation and in template strings, so this works nicely:

let red = colour('#e11')
let myDarkRedElement = `<div style="background:${red.darken()}; color:${red.lighten(0.8)}">Hello</div>`

Colour.complement() → Colour

Inverts the hue value. Nothing fancy.

Colour.invert() → Colour

Inverts lightness and hue.

Colour.darken( amount = 0.1 ) → Colour

Darkens Colour by a percentage of amount.

Colour.lighten( amount = 0.1 ) → Colour

Lightens Colour by a percentage of amount.

Colour.palette( colourspace? = 'oklab' ) → [Colours]

Returns a palette of 11 colours from light to dark, based on the current colour. Both chroma and lightness get adjusted to create a harmonious scale, so the exact original colour might not exist in the list.

Colour.gradient( clr: Colour | cssString | Colour[], type? = 'linear', rotation? = 0, position? = [0.5, 0.5], colourspace? = 'oklab' ) → css gradient string

A simple wrapper around css gradient strings, letting you create dynamic gradients easily.

clr can be either a css string, a Colour, or an array of Colours. The current color is included at the start of the gradient.

Supports a subset of gradient options. Works for 'linear', 'radial' and 'conic' gradients. position has no effect on linear gradients, and rotation has no effect on radial gradients. There's no support for positional values for colours, all colours are added linearly. For fancier gradients, roll your own!

A simple gradient from blackish to whiteish:

let gradient = colour('#111').gradient('#eee')
// returns 'linear-gradient(in oklab 0deg, oklch(17.7638% 0 180 / 1), oklch(94.9119% 0 180 / 1))'

Colour.steps( clr: Colour | cssString, steps? = 1, colourspace? = 'oklab', interpolator? = ö.lerp ) → [Colours]

Interpolates between current colour and colour, in steps, and returns an array of Colours. The start and end values are included in the array, so if steps is 1, the resulting array has three colours.

Lets you do for example:

let html = `<div style="display:flex">${colour('hsl(42.41 100% 56%)')
    .steps('rgb(255, 33, 74)', 10)
    .map(v => `<div style="height:5rem; flex:1 0; background:${v}"></div>`)
    .join('')}</div>`

Colour.mix( clr: Colour | cssString, percent? = 0.5, colourspace? = 'oklab', interpolator? = ö.lerp ) → Colour

Blends two colours together, basically. Use it like this, for example:

let html = ö.map(
    'Fancy effect:',
    (v, i, a) =>
        `<span style="color: ${colour('#000').mix(
            '#FE5C03',
            100 - (100 / a.length) * i,
        )}">${v}</span>`,
)

Colour.getInterpolator( clr: Colour | cssString, colourspace? = 'oklab', interpolator? = ö.lerp ) → function( t ) → Colour

Creates an interpolator function that takes a t value between 0 and 1, and returns the Colour at t between current colour and colour.