Javascript expression in parentheses

var x = (1,2,3);
alert(x);

This expression evaluates to 3.

How is this expression (1,2,3) c开发者_StackOverflowalled? Why does it return 3?

Javascript has a comma operator, like C does. It evaluates each of the expressions, then returns the last one.

I haven't seen this in Javascript before. But in a number of other C'ish languages, it basically evaluates each of the expressions in the parentheses and returns the value of the last one.