Javascript dot after curly bracket syntax error ?: {num: 1} .num

Question

In Chrome devtools, enter the following: {num:1}.numgives a syntax error:

SyntaxError: Unexpected token .

... but entering this returns 1:

(function() {
    return {num:1}.num;
})();

Why am I getting a syntax error in the first example, but not the second?

+3

Web_Designer Feb 07 '14 at 4:58

1 answer

Felix Kling · Answer 1 · 2014-02-07T05:01:12+0000

Since braces in this situation are ambiguous and are interpreted as a block statement , and not as an object literal. Sort of

{
    num: 1
}
.num

Where is num:interpreted as label .

You can use the grouping operator to force the construct to be interpreted as an expression:

({num: 1}).num

, return ( )