jQuery expression as object key

Question

I need to figure out how to create a dynamic key string for an object. This expression makes JavaScript complain.

return {$(this).val(): true};      // returns an object e.g. {2: true}

What am I doing wrong?

adeneo · Accepted Answer · 2014-04-14T12:25:40.770

5

You have to create the object, then use bracket notation for the dynamic key

var obj = {};
var val = $(this).val();

obj[val] = true;

return obj;

or a completely unnecessary one-liner

return (function(o,e) {o[e.value]=true; return o;})({}, this);

edited Apr 14 '14 at 12:25

answered Apr 14 '14 at 12:17

adeneo

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meh. too slow. what adeneo said. – Dbl Apr 14 '14 at 12:18
@AndreasMüller: ditto :P – Amadan Apr 14 '14 at 12:18
Anyway to do this in one line? =) – silkfire Apr 14 '14 at 12:19
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@silkfire: `var obj = {}; var val = $(this).val(); obj[val] = true; return obj;` :P (Serious answer: no) – Amadan Apr 14 '14 at 12:20
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@silkfire: Not directly in an initializer, no. If you absolutely, positively **must** do it where a single expression is needed, you have to use an inline function: `var obj = (function(val) { var o = {}; o[val] = true; return o;})($(this).val());` Normally, of course, you don't want to do that. – T.J. Crowder Apr 14 '14 at 12:21
`return (function(o,e) {o[e.value]=true; return o;})({}, this);` – adeneo Apr 14 '14 at 12:21
Use a function if you want a one-liner. – Florian Margaine Apr 14 '14 at 12:26
Thanks for some great answers, everyone! – silkfire Apr 14 '14 at 12:32

Amadan · Answer 2 · 2014-04-14T12:25:28.850

1

The JavaScript object literal syntax {x: y} specifies that x will be a (possibly) quoteless string, and y any value. You can't use this syntax for dynamic keys.

Use this instead:

var foo = {};
foo[$(this).val()] = true;
return foo;

edited Apr 14 '14 at 12:25

answered Apr 14 '14 at 12:18

Amadan

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There you go. Got my blooper. Sorry Guys :) – loxxy Apr 14 '14 at 12:26

jQuery expression as object key

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