README

Lean JavaScript Utilities as Micro-libraries

This is not another pure functional utility library. These are just a set of common useful patterns that have evolved working with JS.
Unfortunately the existing popular libraries (Underscore, Lodash, Ramda, Trine, is, etc) don't result in readable code that is easy to reason about. Instead of putting the data in the first, second, third argument or context variable, this library favours lambda's (partially applied functions) that complement the native Array operations, not compete with them.

For a flavour of what I mean, see:

// clean all js files in current dir, except reserved, logging before deletion
fs.readdirSync(__dirname)
  .filter(includes('js'))
  .filter(not(is.in(core)))
  .map(prepend(__dirname+'/'))
  .map(log('deleting'))
  .map(fs.unlinkSync)

// from mutation observer, redraw all added nodes that are custom elements
mutations
  .map(key('addedNodes'))
  .map(to.arr)
  .reduce(flatten)
  .filter(by('nodeName', includes('-')))
  .map(ripple.draw)

Each function is in it's own repo. This library just has an automated link to all of them. This has a few benefits:
- You can npm i utilise and finally write imports like <org>/<repo> in each file.
- You don't have to make up esoteric names due to lack of <org>/<repo> in npm.
- You can use utilise.js to import everything (in your application).
- You can use { utility } = require('utilise/pure') to import what you need + tree shake.
- You don't have to load a 0.5MB utility library just to use one function.
- You can be a lot smarter with dead code elimination, even if you include the base file (but not use everything).
There is no spraying your code with _. everywhere, since these functions are largely first-class additions to the grammar of the language that make your code a lot more fluent.
These are mostly stable/fixed, a few new ones may still need experimenting with to get the API right.
A smaller set of high power-to-weight ratio functions are preferred over many, many different functions that do similar things.
Each micro-library is only just a few lines.
Each micro-library has 100% coverage. See badges below.
All browsers (IE >= 9) + node are supported. Tests are run on real browsers using popper.
There is no polyfilling done here. Recommend using polyfill.io where needed. Some libraries will fail tests (like promise) which assume a native API like Promise, unless you shim first.

API Reference

Please also refer to the respective test.js for more cases and examples.

Coverage Status"> all

Select all elements based on a CSS selector, piercing shadow boundaries if the browser supports it.

all('li.class')

Narrow search space by also passing in a node

all('li.class', ul)

Coverage Status"> append

Append something to a string

['lorem', 'ipsum']
  .map(append('-foo')) // returns ['lorem-foo', 'ipsum-foo']

Coverage Status"> args

Cherry-pick arguments to pass to function by index. This is useful when iterating a list, and invoking a function which may be confused if passed the index and array arguments.

['lorem.txt', 'ipsum.txt']
  .map(args(0)(fs.createWriteStream))

This would fail without args since the second argument (index) would try to be read as the encoding.

You can pick out more than one argument using an array instead of a number.

Coverage Status"> attr

Get or set value of element attribute.

attr('key')(el)          // returns value for attribute key
attr('key', 'value')(el) // adds [key=value]
attr('key', false)(el)   // removes attribute key

Coverage Status"> az

Sorts array ascendingly based on the value of a key

array.sort(az('value'))

Since it uses key internally, you can also sort on a deep key.

Coverage Status"> body

Get the value of a resource from a ripple instance

body(ripple)('users')

This is used internally to avoid any type-specific convienience defaults. Always returns undefined if the resource does not exist. You should probably use ripple('resource') to get the value of a resource in your application.

Coverage Status"> by

Checks if a property matches a value

users = [ { name: 'foo' }, { name: 'bar' } ]
users
  .filter(by('name', 'foo'))

If the second value parameter is a function, you can run custom logic against each property (default is ==)

nodes
  .filter(by('nodeName', isCustomElement)) // checks if has '-' in tag

It is common to sometimes see filtering empty values via .filter(Boolean). If only one parameter is given, it filters out objects that do not have a value for the property.

nodes
  .filter(by('prop')) // removes object that do not have a value for prop

Coverage Status"> chainable

Takes a function, and returns a new function that evaluates the original function and also returns it again ignoring what the evaluated function returns

ripple('key', value)                // this normally registers a resource, and returns the value
ripple.resource = chainable(ripple) // ripple.resource now registers a resource, but returns ripple again

ripple 
  .resource('foo', 'bar')
  .resource('lorem', 'ipsum')

NB: I think this will be deprecated in favour of the more generic proxy function that is used to alter return values

Coverage Status"> client

Simple variable: Am I on the server or browser?

// browser
client == true

// server
client == false

Useful for isomorphic apps/libs, and also deadcode elimination.

Coverage Status"> clone

Returns a new deep copy of an object

copied = clone(original)

Coverage Status"> colorfill

Adds color to strings, standardising behaviour across server/client

require('colorfill')

'foo'.red  // server, returns string in red
'foo'.red  // client, returns string

Coverage Status"> copy

Copies properties from one object to another

keys(from)
  .filter(not(is.in(private)))
  .map(copy(from, to))

Coverage Status"> datum

Returns the D3 datum for a node. Useful in lists as you cannot d3.select(node).datum()

nodes
  .map(datum)

Coverage Status"> deb

Lightweight scoped version of console.log with a prefix, useful for per module identification

deb = deb('[module/prefix]')
deb('something went wrong!') // [module/prefix] something went wrong

Returns the input, so it is useful with intermediary logging whilst iterating over a list

list
  .map(op1)
  .map(deb)
  .map(op2)

You can filter debug logs on server-side with DEBUG (module, or module/submodule) or using the debug querystring parameter on the client-side.

Coverage Status"> debounce

Returns a debounced function. Specify time in ms, or defaults to 100ms.

debounced = debounce(fn)
// or
debounced = debounce(200)(fn)

Coverage Status"> def

Defines a property, if does not already exist, returning the value

def(object, prop, value[, writable])  // returns value

Coverage Status"> defaults

Sets default values for properties on an object if not already defined. Normally used at the beginning of components to default state values and expose API:

var state = defaults(this.state, {
  values: []
, focused: true
})  

// state.focused == this.state.focused == true
// state.values  == this.state.values  == []

To idempotently define API on an element:

defaults(this, { toggle, spin })  

// this.spin()
// this.toggle()

In case you need to default and reference a property for another property, you can default them individually rather than via an object literal.

defaults(state, 'numbers', [1,2,3,4,5])
defaults(state, 'odd', state.numbers.filter(d => d % 2))

// state.numbers == [1,2,3,4,5]
// state.odd == [1,3,5]

Coverage Status"> delay

Creates a promise that eventually delays after the specified milliseconds. You can also set to resolve to a specific value.

await delay(1000)
await delay(1000, 'some value')

Coverage Status"> done

Given a versioned object, attaches a one-time callback for a response on the latest change. This is an alternative and more robust pattern than using random correlation ID's to link request-responses over a decoupled channel.

done(push(newUser)(users))
  (d => !d.invalid && showConfirmation())

Coverage Status"> el

Creates a node from a CSS selector

el(div.foo.bar[lorem=ipsum]) // returns <el class="foo bar" lorem="ipsum" />

Coverage Status"> emitterify

Enhance any object with .on, .once and .emit

var o = emitterify({}) 
o.on('event')             // get listeners for event
o.on('event', fn)         // set listener on arbitrary event
o.once('event', fn)       // set listener that is only called once
o.on('event.ns', fn)      // set listener for event.namespace, unique listener per namespace
o.emit('event', payload)  // emit event with optional payload
o.emit('event', [array])  // emit event with optional multiple arguments

Coverage Status"> err

Lightweight scoped version of console.error with a prefix, useful for per module identification

err = err('[module/prefix]')
err('something went wrong!') // [module/prefix] something went wrong

Coverage Status"> escape

Escapes HTML

escape = escape('<div></div>') // '&lt;div&gt;&lt;/div&gt;'

Coverage Status"> extend

Extends an object with properties from another, not overwriting properties by default. See also extend.

to = { foo: 1 }
from = { foo: 2, bar: 3 }
extend(to)(from)  // to == { foo: 1, bar: 3 }

Coverage Status"> falsy

Function that returns false

shouldIContinue = falsy // when executed, returns false

Coverage Status"> file

Reads and returns a file. Server only.

var template = file('template.html')

Coverage Status"> filify

Browserify transform that resolves file('filename') to the actual file

file('foo') // converted to a string containing the contents of the file foo

Coverage Status"> filter

Filters an array

once(tr, filter(isEven))

Coverage Status"> first

Returns first element in array

first(array)  // returns array[0]

Coverage Status"> flatten

Flattens a 2D array

twoD = [[1], [2], [3]]
oneD = twoD.reduce(flatten)  // [1, 2, 3]

Coverage Status"> form

Converts a <form> to a JSON object as you would expect. This is useful to abstract the different ways of getting values from different controls (text inputs, radio elements, checkboxes, selects, files, custom elements). The keys come from the name attributes. Checkboxes are represented as arrays. Files as FileList. For Custom Elements, it takes the element.state.value property, so they can also participate in forms.

const { values, invalid } = form(element)

values == {
  foo: '..'         // text inputs, radio elements, selects as single value
, bar: ['..', '..'] // checkboxes as arrays
, baz: FileList     // file inputs   
}

invalid is an array containing all the elements that were marked by the is-invalid class.

Coverage Status"> fn

Turns a function as a string into a real function

foo = 'function(){ console.log("Hi!") }'
foo = fn(foo)   // returns function(){ console.log("foo") }
foo()           // logs out "Hi!"

Coverage Status"> from

Looks up and returns a property from an object. Useful for converting foreign keys to matching records.

users = [
  { name: 'foo', city: 1 }
, { name: 'bar', city: 2 }
, { name: 'baz', city: 1 }
]

cities: { 1: 'London', 2: 'New York', 3: 'Paris' }

// get a unique list of cities users live in
users
  .map(key('city'))
  .map(from(cities))
  .filter(unique)     // returns [ 'London', 'New York' ]

from.parent returns the value of a property from the parent datum. Useful if you generate a fixed number of columns, whose values depend on the parent.

processes = [ 
  { name: 'chrome', pid: '123', cpu: '50%' } 
, { name: 'safari', pid: '456', cpu: '50%' } 
]

// generate a list of rows, each with three columns
once('tr', processes)
  ('td', ['name', 'pid', 'cpu'])
    .text(from.parent)

<tr>
  <td>chrome</td><td>123</td></td>50%</td>
</tr>
<tr>
  <td>safari</td><td>456</td></td>50%</td>
</tr>

In general you should try to pass each element the data it needs and not reach outside of its own scope.

Coverage Status"> group

Grouped logging using groupCollapsed/groupEnd if it exists, or simple start/end demarcation logs using asterisk if not.

group('category', fn)

Coverage Status"> grep

Conditionally executes a function depending on the regex against its arguments. Returns the original unfiltered function. Useful for higher order modules to conditionally filter out logs of many smaller modules unobtrusively.

// filter out all internal logs from ripple (i.e. that don't start with "[ri/")
unfiltered = grep(console, 'log', /^(?!.*\[ri\/)/)

Coverage Status"> gt

Filters array depending if value of a key is greater than a threshold.

array.filter(gt(100, 'value'))

Since it uses key internally, you can also filter on a deep key.

Coverage Status"> has

Checks if object has property using in keyword

has(object, 'prop')

Coverage Status"> hashcode

Converts string to unique numerical equivalent - same as Java hashcode function.

hashcode('foobar') // -1268878963

Coverage Status"> header

Extract the value of a header from a ripple resource

header('content-type')(resource) // returns for example 'application/javascript'

Or if a second parameter is set, check for equality

// filter to get all data resources
resources 
  .filter(header('content-type', 'application/data'))

Coverage Status"> identity

Identity function, returns what it is passed in

identity(5) // returns 5

Coverage Status"> iff

Only invoke second function if condition fulfilled. Useful for finer-grained control over skipping certain operations

sel(el).property('value', iff(cond)(setValue))

Coverage Status"> includes

Checks if string or array contains the pattern or element (uses indexOf common to strings and arrays)

// filter down to all javascript files
files
  .filter(includes('.js'))

Coverage Status"> is

Various basic flavours of checking

is(v)(d)      // equality d == v
is.fn         // function
is.str        // string
is.num        // number
is.obj        // object (includes arrays)
is.lit        // object (excludes arrays)
is.bol        // boolean
is.truthy     // truthy
is.falsy      // falsy
is.arr        // array
is.null       // null
is.def        // undefined
is.promise    // promise
is.in(set)(d) // checks if d in set (string, array or object)

Coverage Status"> join

Replace a foreign key property with the full record or a value from the record

// doctors == [ { name: nick, grade: 1 .. }, .. ]
// ripple('grades') == [ { id: 1, name: 'FY1' }, { id: 2, name: 'SHO' }, .. ]

doctors
  .map(join('shift', 'shifts'))
  .map(join('speciality', 'specialities'))
  .map(join('grade', 'grades.name'))
  .map(join('hospital', 'hospitals.location'))

// you can use with array map to replace ids with corresponding records
[1, 2, 3]
  .map(join('grades')) // returns [ { .. }, { .. }, { .. } ]

// you can use without ripple, if the table (last parameter) is a string 
// it'll resolve from ripple, but if it's a vanilla array, it'll just use that
[1, 2, 3]
  .map(join(grades)) // returns [ { .. }, { .. }, { .. } ]

If the second parameter is a string, it uses that as the ripple resource to look in. You can also use a primitive array outside of a ripple context.

Coverage Status"> key

Powerful versatile operator for accessing/setting key(s)

key('name')(d)                        // returns value of property name from object d
key(d => d.first + d.last)(d)         // returns computed value
key('details.profile.name')(d)        // returns deep property
key('details', 'foo')(d)              // set property
key('details.profile.name', 'foo')(d) // set deep property
key(['name', 'city.name'])(d)         // returns object with selected keys (can mix from any level)
key()(d)                              // returns object root if key undefined

Accessing deep keys returns undefined if a link is missing, which prevents doing things like:

(((d || {}).details || {}).profile || {}).name

Setting a deep key will create any missing keys it needs as it traverses the path.

If the second value parameter is a function, it evaluates it with the data before setting.

To make dates in all records human-readable with moment for example:

orders = [ { .. }, { .. } ]
orders
  .map(key('date', mo.format('MMM Do YY')))

Coverage Status"> keys

Alias for Object.keys

keys({ foo: 1, bar: 2}) // returns ['foo', 'bar']

Coverage Status"> last

Returns the last element in the array

last(array) // returns array[array.length-1]

Coverage Status"> link

Links changes in the attribute of one component to the attribute of another

// when a different day is selected in the calendar, the detail page automatically updates
link('events-calendar[selected-day]', 'event-detail[day]')

<events-calendar selected-day="1-1-1970" />
<event-detail day="1-1-1970"/>

Coverage Status"> lo

Lowercase a string

['A', 'B', 'C'].map(lo) // returns ['a', 'b', 'c']

Coverage Status"> log

Lightweight scoped version of console.log with a prefix, useful for per module identification

log = log('[module/prefix]')
log('something went wrong!') // [module/prefix] something went wrong

Returns the input, so it is useful with intermediary logging whilst iterating over a list

list
  .map(op1)
  .map(log)
  .map(op2)

Coverage Status"> lt

Filters array depending if value of a key is less than a threshold.

array.filter(lt(100, 'value'))

Since it uses key internally, you can also filter on a deep key.

Coverage Status"> mo

Convenience functions working with moment

dates.map(mo)                     // convert to moment object
dates.map(mo.format('Do MMM YY')) // convert to specific format
dates.map(mo.iso)                 // convert to iso date format

Coverage Status"> noop

Function that does nothing

;(fn || noop)()

Coverage Status"> not

Negates the result of a function

numbers
  .filter(not(isEven))
  .filter(not(is('5')))

Coverage Status"> nullify

Converts a truthy/falsy to true/null. This is a useful utility for D3 functions which expect a null value to remove as opposed to just a falsy.

selection
  .attr('disabled', nullify(isDisabled))

Coverage Status"> once

Function for building entirely data-driven idempotent components/UI with D3.

once(node)                        // limit to this node
  ('div', { results: [1, 2, 3] }) // creates one div (with the specified datum)
    ('li', key('results'))        // creates three li (with datum 1, 2, 3 respectively)
      ('a', inherit)              // creates anchor in each li (with parent datum)
        .text(String)             // sets the text in anchor to the datum

The first time you call once(node | string) it essentially selects that element and limits the scope of subsequent operations to that.

Subsequents calls generate a D3 join using the syntax (selector, data). The selector can be:

A selector string (foo.bar.baz). Classes are fine too and will be added to the final elements created.
A real element, which will be replicated.
A function, which will be given parent data, in case you wish to output different (custom) elements based on data.

The data is the same as what you would normally use to generate a join (array of items, or function), with some convenient defaults: if you pass an object, number or boolean it'll be converted to a single-valued array, meaning "create one element with this as the datum". If you pass in a falsy, it defaults to empty array "meaning removing all elements of this type".

The return value is essentially a D3 join selection (enter/update/exit), so you can continue to customise using .text, .classed, .attr, etc. You can also access the elements added via .enter and removed via .exit.

There are two further optional arguments you can use (selector, data[, key[, before]]). The key function has the exact same meaning as normal (how to key data), which D3 defaults to by index. The before parameter can be used to force the insertion before a specific element à la .insert(something, before) as opposed to just .append(something).

Once will also emitterify elements as well as the selection so you can fluently listen/proxy events. You can create custom events, use namespaces for unique listeners, and listeners on events like "click" will trigger from both real user interaction from the DOM as well as via .emit.

once('list-component', 1)
  .on('selected', d => alert(d))

once('list-component')
  ('.items', [1,2,3])
    .on('click', d => this.parentNode.emit('selected', d))

Coverage Status"> overwrite

Extends an object with properties from another, overwriting existing properties. See also extend.

to = { foo: 1 }
from = { foo: 2, bar: 3 }
overwrite(to)(from)  // to == { foo: 2, bar: 3 }

Coverage Status"> owner

Either window or global dependeing on executing context

// browser
owner == window

// server
owner == global

Coverage Status"> parse

Equivalent to JSON.parse

Coverage Status"> patch

Updates multiple values at a key, updates the internal log (if versioned), and emits a standardised change event (if emitterified). See also other functional versioned operators.

patch('key', { a, b, c })(object)

Coverage Status"> pause

Actually pauses a stream so you can build up a pipeline, pass it around, attach more pipes, before starting the flow. Server only.

var stream = pause(browserify)
  .pipe(via(minify))
  .pipe(via(deadcode))

addMorePipes(stream)

function addMorePipes(stream){
  stream
    .on('end', doSomething)
    .pipe(file)
    .flow()
}

Coverage Status"> perf

Completely unobtrusive way to evaluate how long a function takes in milliseconds.

If you have the following function call:

fn(args)

You wrap a perf around fn to see how long it takes:

perf(fn)(args)  // Evaluates the function, logs the time taken in ms, and returns same value original fn would

You can also add an optional message to the log:

perf(fn, 'foo')(args)

Coverage Status"> pop

Pops an element from an array, updates the internal log (if versioned), and emits a standardised change event (if emitterified). See also other functional versioned operators.

pop(users)

Coverage Status"> prepend

Prepend something to a string

['foo', 'bar']
  .map(prepend('hi-'))  // returns ['hi-foo', 'hi-bar']

Coverage Status"> promise

Convenience functions for working with (native) Promises

var p = promise()                 // creates promise with resolve/reject attached
p.resolve('result')
p.reject('something went wrong')

promise(5)                        // creates promise and resolves to value
promise.args(1)('foo', 'bar')     // creates promise that resolves to argument given
promise.sync(1)('foo', 'bar')     // creates thenable that immediately invokes then callback
promise.noop()                    // creates empty promise
promise.null()                    // creates promise that resolves to null

Coverage Status"> proxy

Proxy a function. It is common to use fn.apply(this, arguments) for proxying. This function allows you to do that, but alter the return value and/or context.

proxy(fn, 5)      // returns a function that invokes fn, but then always returns 5
proxy(fn, 5, {})  // same as above, but also changes context variable

This is also useful for functional inheritance:

bill.total = proxy(bill.subtotal, bill.vat)

Coverage Status"> push

Pushes an element to an array, updates the internal log (if versioned), and emits a standardised change event (if emitterified). See also other functional versioned operators.

push({ firstname: 'foo', lastname: 'bar' })(users)

Coverage Status"> ready

Calls the function once document.body is ready or immediately if it already is

ready(fn)

Coverage Status"> raw

Select an element based on a CSS selector, piercing shadow boundaries if the browser supports it.

raw('.foo')

Narrow search space by also passing in a node

raw('li', ul)

Coverage Status"> rebind

D3 rebind function to rebind accessors. See the docs here.

Coverage Status"> remove

Removes a key from an object, updates the internal log (if versioned), and emits a standardised change event (if emitterified). See also other functional versioned operators.

remove('key')(object)

Coverage Status"> replace

Replace a value in a string

['Hi name', 'Bye name']
  .map(replace('name', 'foo'))

Coverage Status"> resourcify

Returns the specified resource from a ripple instance. Returns an object of resources if multiple specified. Returns undefined if one of the resources not present.

resourcify(ripple)('foo')         // returns body of foo
resourcify(ripple)('foo bar')     // returns { foo: foo-body, bar: bar-body }
resourcify(ripple)('foo bar baz') // returns undefined, since no baz resource

Coverage Status"> sall

Convenience function for d3.selectAll. If either argument is already a D3 selection, it will not double wrap it.

sall(parent)(selector)

Parent/selector can be selection/string/node. If no parent, selects globally.

Coverage Status"> sel

Convenience function for d3.select. If the argument is already a D3 selection, it will not double wrap it.

sel(string)

Coverage Status"> send

Sends a file on an express route. Server only.

app.get('/file', send('./file'))

Coverage Status"> set

Takes an atomic diff and applies it to an object, updating the internal log, and emitting a standardised change event (if emitterified). An atomic diff is an object in the format { type, key, value, time } where type can be either of add | update | remove.

set({ key, value, type })(object)

If there is no diff, it initialises object with the .log property:

set()(object[[, existing], max])

If an existing object is specified with a .log property, it will branch off that history to create the new .log property. If a max property is specified, there are three options:

0: Diffs will be pushed onto the .log
= 0: The .log property will always be []
< 0: Nulls will be pushed onto the .log (this is to avoid potentially expensive operations in the critical path, whilst still being able to use .log.length as a revision counter)

Note that this, as will all utilities here, is fully graceful and will work with:

A vanilla object - just applies diff
An emitterified object i.e. has a .on/.emit - applies the diff and emits log event
An emitterified, versioned object (has a .log) - applies diff, emits event, and updates immutable/diff log

See also the more ergonomic functional versioned operators which use this generic operator, but set most of the values for you:

Coverage Status"> slice

Slice all strings in an array

['Hi name', 'Bye name']
  .map(slice(0, 2)) // ['Hi', 'By']

Coverage Status"> sort

Sorts elements in an array

once('tr', sort(Boolean))

Coverage Status"> split

Split items

['a.b', 'b.c'].map(split('.')) // returns [['a','b'], ['b','c']]

Coverage Status"> str

Coerces anything into a string

str(5)                // returns '5'
str({ foo: 5 })       // returns '{ foo: 5 }'
str(undefined)        // returns ''
str(function(){ .. }) // returns 'function(){ .. }'

Coverage Status"> stripws

Strips the whitespace between tags (but not between attributes), which is useful to make declarative testing less brittle and less sensitive

stripws`
  <div>
    foo
  </div>
`         
// <div>foo</div>

stripws('<a>\n   <b>')  
// '<a><b>'

Coverage Status"> tdraw

Simple stub for the draw function to test components. Takes a DOM element, a render function and some initial state. Sets the initial .state, the .draw function and renders the element.

t.plan(2)

const host = tdraw(el('ux-button'), button, { label: 'foo', spinning: true })

host.spin(true)
t.ok(includes(`class="is-spinning"`)(host.outerHTML))

host.spin(false)
t.notOk(includes(`class="is-spinning"`)(host.outerHTML))

Coverage Status"> th

Invokes a function with the this variable, then the arguments. Useful for using arrow syntax with functions that need the context variable.

// instead of:
// input.on('keyup', log)
// function log(){
//  console.log(this.value)
// }

const log = el => d => console.log(el.value)
input.on('keyup', th(log))

Coverage Status"> time

Alias for setTimeout with duration as first parameter for better readability

time(10, function(){ .. })
time(20, function(){ .. })
time(30, function(){ .. })

Coverage Status"> to

to.arr: Converts to a primitive type (only real arrays)

to.arr(NodeList)
to.arr(arguments)

to.obj: Converts an array to an object. Uses id property as key by default if none specified. The key can also be a function which will receive the item and it's index as parameters, and return the computed string to use as the key.

[
  { id: 'foo', value: 1 }
, { id: 'bar', value: 2 }
].reduce(to.obj, {})

/* returns 
{ 
  foo: { id: 'foo', value: 1 }
, bar: { id: 'bar', value: 2 }
} 
*/

// or you can use .reduce(to.obj('prop'), {})

Note: You should always use an initial value with the reduce function. This is because if your array happens to be an array with only one element and there is no initial value, JavaScript will not even call the reduce function.

Coverage Status"> unique

Filter an array to unique values

[1,1,2,3].filter(unique, 1) // returns [1,2,3]

Coverage Status"> update

Updates a value at a key, updates the internal log (if versioned), and emits a standardised change event (if emitterified). See also other functional versioned operators.

update('key', value)(object)

Coverage Status"> values

Converts an object to array

values({ 
  a: { name: 'foo', value: 1 }
, b: { name: 'bar', value: 2 }
})

/* returns
[ 
  { name: 'foo', value: 1 }
, { name: 'bar', value: 2 }
]
*/

Coverage Status"> via

Buffers output to a stream destination. Useful when you need the whole input rather than chunks. Server only.

stream
  .pipe(via(minify))
  .pipe(via(replace))

Coverage Status"> wait

Only invoke handler if condition fulfilled. Useful for determining execution based on declarative pattern matching.

o.once(wait(msg => msg.id)(handler))

Coverage Status"> wrap

Wraps something in a function which returns it when executed

wrapped = wrap(5)
wrapped()          // returns 5

Usage no npm install needed!