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JavaScript: call invo-cursion?
// OOP
console.log( 'OHAI'.blink() );
// Call invocation
console.log('OHAI') );
// $ always makes things look awesome.
var $ =;
// Very explicit call invocation
console.log( $.call(String.prototype.blink, 'OHAI') );
// Very, very explicit call invocation, ie. call invo-cursion?
console.log( $.call($,$,$,$,$,$,$,$,$,$,$,$, String.prototype.blink, 'OHAI') );
// ^^^^^^^^^^^^^^^^^^^^^^^ "bonus" calls
// You can have fun with apply invocation and _ too.
var _ = Function.prototype.apply;
// Very, very explicit apply invocation, ie. apply invo-cursion.
console.log( _.apply(_,[_,[_,[_,[_,[_,[_,[_, [ String.prototype.blink, ['OHAI'] ]]]]]]]]) );
// ^^^^^^^^^^^^^^^^^^^^^^ "bonus" applies, and fun w/brackets ^^^^^^^^

That enables a very easy way to create number lists:

$.call(_, Array, 0, new Array(5)).map($, parseInt)
// 0, 1, 2, 3, 4

@ricardobeat I had no idea that Array.apply(null, new Array(5)) would return a non-sparse array. Very cool!


Also @ricardobeat, I'd probably do something more like this (just in general) to create a number list:

Array.apply(null, {length: 5}).map(, Number) // [0, 1, 2, 3, 4]

In the vein of .map(, Number) this function will swallow n leading function arguments:

function swallow(n, fn) {
  return n ? swallow(n - 1, : fn;

function log(a, b, c) {
  console.log([a, b, c]);

log(6, 7, 8)              // [ 6, 7, 8 ]

swallow(1, log)(6, 7, 8)  // [ 7, 8, undefined ]
swallow(2, log)(6, 7, 8)  // [ 8, undefined, undefined ]
swallow(3, log)(6, 7, 8)  // [ undefined, undefined, undefined ]

In that way of creating number lists it can be misleading to write, I would suggest to point to a more generic location like the Function constructor:

Array.apply(null, {length: 5}).map(, Number) // [0, 1, 2, 3, 4]

So its more explicit that you can use any other function:

Array.apply(null, {length: 5}).map(, Math.exp) // [1, 2.71, 7.38, 20.08, 54.59]

But if you need the numbers as strings and performance is a priority you are better off using Object.keys instead of the String constructor:

keys(Array.apply(null, {length: 5})) // ["0", "1", "2", "3", "4"]

@AltIvan while using a more generically-located Function#call isn't a bad idea, is no more generic than as both Function and Number are constructor functions. What you meant to suggest was which is the prototype object on which Function#call is actually defined.

Array.apply(null, {length: 5}).map(, Number) // [0, 1, 2, 3, 4]

That being said, it's a moot point, as and are all references to the same function.


// Indices as strings.
Array.apply(null, {length: 5}).map(, String) // ["0", "1", "2", "3", "4"]
// Number list.
Object.keys(Array.apply(null, {length: 5})).map(Number) // [0, 1, 2, 3, 4]

on very old/obscure versions of webkit

Array.apply(null, {length: N}) 

may not work, returns something like

[object Object] is not a valid argument for Function.prototype.apply

However, on the old/obscure version I'm testing on (id's itself as Safari 5.x but it isn't),

Array.apply(null, Array(n)) 

does work.

{length: N} also seems to fail in PhantomJS, whereas Array(N) doesn't


Hey, cool stuff, but can someone please explain me how's new Array(5) is equivalent to {length: 5}, and where's {length: 5} coming from in terms of Array constructor parameters if understand this right?


Regarding Array(n):

When Array is called as a function rather than as a constructor,
it creates and initialises a new Array 

taken with courtesy from Annotated ECMAScript 5.1


@vsternbach {length: 5} is an array-like for apply function

From MDN docs:


fun.apply(thisArg, [argsArray])


The value of this provided for the call to fun. Note that this may not be the actual value seen by the method: if the method is a function in non-strict mode code, null and undefined will be replaced with the global object, and primitive values will be boxed.
An array-like object, specifying the arguments with which fun should be called, or null or undefined if no arguments should be provided to the function. Starting with ECMAScript 5 these arguments can be a generic array-like object instead of an array. See below for browser compatibility information.

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