Why after executing that snippet of code:
var a = {};
var b = {};
var g = {};
g[a] = "aa";
g[b] = "dd";
the value of g[a] is "dd"?
a == b is false so what is going on here?
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JavaScript implementations might have some bizarre-hidden-ones. Which Browser / JavaScript engine are you testing with?JWL– JWL2011-04-24 15:39:47 +00:00Commented Apr 24, 2011 at 15:39
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2 Answers
JavaScript object keys can only be strings. When you store g[a] = 'aa', a is converted to a string using the toString() method,1 so you're actually storing 'aa' at g[a.toString()].
In this case, a.toString() is '[object Object]', which is equal to b.toString().
To make it really obvious, the code in your question is equivalent to this:
var g = {};
g['[object Object]'] = 'aa';
g['[object Object]'] = 'dd';
Moral of the story: just don't try to use anything other than strings as property names.
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a and b are objects, and you'd be using them as keys in doing g[a] or g[b], which can't work since associative arrays can only use valid variable names or strings as keys.
What are you trying to accomplish?
var a = "a";
var b = "b";
var g = {};
g[a] = "aa";
g[b] = "dd";
Would work properly, however.
