Why provide an array argument in Javascript's array.forEach callback?

Question

Javascript\'s array iteration functions (forEach, every, some etc.) allow you to pass three arguments: the current item, the current i

Answer 1

It is possible that you want to pass a generic function as an argument to forEach and not an anonymous function. Imagine a situation where you have a function defined like that:

function my_function(item, i, arr) {
    // do some stuff here
}

and then use it on different arrays:

arr1.forEach(my_function);
arr2.forEach(my_function);

The third argument allows the function to know which array is operating on.

Another case where this might be usefull, is when the array has not been stored in a variable and therefore does not have a name to be referenced with, e.g.:

[1, 2, 3].forEach(function(item, i, arr) {});