function

Function(al) utilities.

Table of Contents #

bind(fn, context, [...args]):Function #

Return a function that will execute in the given context, optionally adding any additional supplied parameters to the beginning of the arguments collection.

Arguments

  1. fn (Function) : Target Function
  2. context (Object) : Execution context (object used as this)
  3. [...args] (*) : Arguments (0...n arguments)

See: partial(), object/bindAll

compose(...fn):Function #

Returns the composition of a list of functions, where each function consumes the return value of the function that follows. In math terms, composing the functions f(), g(), and h() produces f(g(h())).


function add2(x) { return x + 2 }
function multi2(x) { return x * 2 }
map([1, 2, 3], compose(add2, multi2)); // [4, 6, 8]

//same as
map([1, 2, 3], function(x){
    return add2( multi2(x) );
});

debounce(fn, delay[, isAsap]):Function #

Creates a function that will delay the execution of fn until after delay milliseconds have elapsed since the last time it was invoked.

Subsequent calls to the debounced function will return the result of the last fn call.


// sometimes less is more
var lazyRedraw = debounce(redraw, 300);
foo.on.resize.add(lazyRedraw);

In this visualization, | is a debounced-function call and X is the actual callback execution:

Default
||||||||||||||||||||||||| (pause) |||||||||||||||||||||||||
                         X                                 X

Debounced with `isAsap == true`:
||||||||||||||||||||||||| (pause) |||||||||||||||||||||||||
X                                 X

You also have the option to cancel the debounced call if it didn't happen yet:


lazyRedraw();
// lazyRedraw won't be called since `cancel` was called before the `delay`
lazyRedraw.cancel();

See: throttle()

func(name):Function #

Returns a function that calls a method with given name on supplied object. Useful for iteration methods like array/map and array/forEach.

See: prop()


// will call the method `getName()` for each `user`
var names = map(users, func('getName'));

partial(fn, [...args]):Function #

Return a partially applied function supplying default arguments.

This method is similar to bind, except it does not alter the this binding.

Arguments

  1. fn (Function) : Target Function
  2. [...args] (*) : Arguments (0...n arguments)

See: bind()


function add(a, b){ return a + b }
var add10 = partial(add, 10);
console.log( add10(2) ); // 12

prop(name):Function #

Returns a function that gets a property with given name from supplied object. Useful for using in conjunction with array/map and/or for creating getters.

See: array/pluck()


var users = [{name:"John", age:21}, {name:"Jane", age:25}];
// ["John", "Jane"]
var names = map(users, prop('name'));

series(...fn):Function #

Returns a function that will execute all the supplied functions in order and passing the same parameters to all of them. Useful for combining multiple array/forEach into a single one and/or for debugging.


// call `console.log()` and `doStuff()` for each item item in the array
forEach(arr, series(console.log, doStuff));

throttle(fn, interval):Function #

Creates a function that, when executed, will only call the fn function at most once per every interval milliseconds.

If the throttled function is invoked more than once during the wait timeout, fn will also be called on the trailing edge of the timeout.

Subsequent calls to the throttled function will return the result of the last fn call.


// sometimes less is more
var lazyRedraw = throttle(redraw, 300);
foo.on.resize.add(lazyRedraw);

In this visualization, | is a throttled-function call and X is the actual fn execution:

||||||||||||||||||||||||| (pause) |||||||||||||||||||||||||
X    X    X    X    X    X        X    X    X    X    X    X

You also have the option to cancel the throttled call if it didn't happen yet:


lazyRedraw();
setTimeout(function(){
    lazyRedraw();
    // lazyRedraw will be called only once since `cancel` was called before
    // the `interval` for 2nd call completed
    lazyRedraw.cancel();
}, 250);

See: debounce()

timeout(fn, millis, context, [...args]):Number #

Functions as a wrapper for setTimeout. Calls a the function fn after a given delay millis in milliseconds. The function is called within the specified context. The return value can be used to clear the timeout using clearTimeout.


var id = timeout(doStuff, 300, this);

clearTimeout(id);

times(n, callback, [context]):void #

Iterates over a callback n times.

Arguments

  1. n (Number) : Number of iterations
  2. callback (Function) : Closure executed for every iteration
  3. context (Object) : Execution context (object used as this)

var output = '';
times(5, function(i) {
    output += i.toString();
});
// output: 01234

For more usage examples check specs inside /tests folder. Unit tests are the best documentation you can get...

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