Question

Since it is possible to do:

var x = 'foo', y = 'foo';

Would this also be possible?

var x, y = 'foo';

I tried it, however x becomes undefined.

I know this may seem like a silly or redundant question, but if I’m curious about something, why not ask? Also you will probably wonder why I would need two variables equal to the same thing in scope. That is not the point of the question. I’m just curious.

Answer 1

You need two separate statements to get the exact same semantics.

var x, y; x = y = 'foo';
// or
var x = 'foo'; var y = x;
// or
var y; var x = y = 'foo';

The solution other users are suggesting is not equivalent as it does not apply the var to y. If there is a global variable y then it will be overwritten.

// Overwrites global y
var x = y = 'foo';

It is a good practice to correctly apply var to local variables and not omit it for the sake of brevity.