JavaScript Array#map: index argument

Question

My question is about the map method of arrays in JavaScript.

You can pass it a function that takes a second argument, the index of the current element of th

Answer 1

Sometimes the index of the element matters. For example, this map replaces every second element with 0:

var a = [1, 2, 3, 4, 5, 6];
var b = a.map(function(el, index) {
    return index % 2 ? 0 : el;
});
console.log(b);

Output:

[1, 0, 3, 0, 5, 0]