When (and why) is {} undefined in a JavaScript console?
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Published on 2012-03-29T22:21:46Z
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In the console of both FF and Chrome, {} is considered undefined until explicitly evaluated:
{}; // undefined
({}); // ? Object
Actually, it's a bit less defined than undefined -- it's apparently bad syntax:
{} === undefined; // SyntaxError: Unexpected token ===
{}.constructor; // SyntaxError: Unexpected token .
But not if it's on the other side, in which case it's fine:
"[object Object]" == {}.toString(); // true
Or if it's not the first expression:
undefined + undefined; // NaN
{} + undefined; // NaN
undefined + {}; // "undefined[object Object]"
What gives?
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