Question

In JavaScript (x, x1, x2, …, xn) always returns xn.

In Python this code is called tuple and it returns different values.

My question is what is the purpose of this code in JavaScript?
Do you have some practical example?

Answer 1

The comma operator evaluates every operand but only returns the result of the last evaluation. It can be used to initialize multiple variable in a for loop.

var str = "Hello, World!";
for(var i = 0, len = str.length; i < len; i++)
    console.log(str.charAt(i));

Edit: As pointed out in the comments, this isn’t a true example of the comma operator, this is just the var. You can see this page for actual examples.