Why reading an array with more than index doesn't throw an error?

Question

I work on web site with pre-existent javascript code.

I found out that in this code, it used to retrieve an array item in this way:

var value = myArray[0, 1];

The result is the second field of the array, but I can't understand the difference with a code like:

var value = myArray[1];

I have tried to change the number before comma but nothing change, it reads always the second item of the array.

It's the JavaScript comma operator. A series of expressions separated by commas evaluates all of them, but the overall value of the series is the value of the *last* expression. Thus, in `0, 1` there are two expressions, and the last one is `1`. — Pointy, Dec 17 '18 at 13:49

score 2 · Accepted Answer · answered Dec 17 '18 at 13:51

2

The comma operator evaluates each of its operands (from left to right) and returns the value of the last operand. That's why you get 1.

answered Dec 17 '18 at 13:51

devedv

1 Answers1