Prototype Function call and bind

Question

Can someone explain logic behind

Function.prototype.call.bind(Array.prototype.forEach);

As I read 'bind' function give to function on which is called a context of object in which to executs.

But in this case bind receive function. So according to me this is not intuitive syntax. If i have further

 myOtherFunction.call(this)

is call is still connected with context of forEach?

Answer 1

Array.prototype.forEach is a method, bound to the context of an array. So you could easily iterate over an array like:

 [1,2,3].forEach(function(x){ console.log(x) })

This is equivalent to:

[].forEach.call([1,2,3],function(x){ console.log(x) })

So you are passing [1,2,3] as the current context ( this ) of your call into forEach() .

What Function.prototype.call.bind(Array.prototype.forEach); does is calling ( call ) the bind function with another function ( Array.prototype.forEach ) as its current context to a variable.

var forEach=Function.prototype.call.bind(Array.prototype.forEach);

means literally spoken: »If a function call on forEach is made, please call it like you would, if you were in the context of Array.prototype.forEach .« It is a shortcut to [].forEach.call(this,function)

For further references see MDN on Function.prototype.call() , Function.protoype.bind() .