Use of colon operator ':' in javascript

Question

Why

asdf:'qwer'

returns qwer, but

var a = asdf: 'qwer';

returns SyntaxError: Unexpected token : ?

Friendly speaking I don't know why asdf:'qwer' doesn't return syntax error. — kotapaulta
– kotapaulta, Commented Jul 22, 2014 at 9:18
I knew about ternary operators. This code was added accidentally before return{zxcv:'cvbn'} and I wonder why browser doesn't return syntax error — kotapaulta
– kotapaulta, Commented Jul 22, 2014 at 9:25

Frédéric Hamidi · Accepted Answer · 2014-07-22 09:18:22Z

1

There is no colon operator in Javascript (except as part of the ternary conditional operator ?:).

In your first snippet, asdf: is a label. In your second one, it's a syntax error, because labels are only valid before statements, not inside expressions.

answered Jul 22, 2014 at 9:18

Frédéric Hamidi

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Valentin Mercier · Accepted Answer · 2014-07-22 09:19:28Z

0

Because it can be used as a label. You can tag for example a loop so you can easily break a superior one, but it has to be a separate command:

MAIN:
while (a) {
  while (b) {
    break MAIN;
  }
}

But obviously you can add a label to anything even if it's useless.

edited Jul 22, 2014 at 9:19

Valentin Mercier

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answered Jul 22, 2014 at 9:18

Razem

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