Yeah, it works in my firebug console. Why does something like this present no syntax error?
[] = 5; [] = doThis(); [] = (function() {})();
Just curious about why it's allowed.
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It is an error in Chrome btw...I think it's just ignoring your setting and moving on along.Nick Craver– Nick Craver2010-07-07 01:43:49 +00:00Commented Jul 7, 2010 at 1:43
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2 Answers
Looks like Javascript in FF allows assignment using matching so you can set multiple variables in one shot:
[x,y] = [5,6]; // sets x to 5 and y to 6
"Obviously", some JS implementations are very forgiving, and will silently ignore any extra values, so this does the same:
[x,y] = [5,6,7];
and this would just not assign anything:
[] = [5,6,7];
and on top of that, it looks like FF is even willing to go with a case that doesn't match an array at all:
[x] = 5; // makes x undefined
so if you use [] = whatever then "nothing gets assigned an undefined value", so it boils down to just evaluating the RHS.
(Disclaimer: this is all just guessing the meaning by running stuff in FF...)
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Dagg Nabbit
There's a detailed thread about mozilla's destructuring assignment syntax here: stackoverflow.com/questions/204444/…
I get a "Uncaught ReferenceError: Invalid left-hand side in assignment" in Chrome. IE8 throws "Error: Cannot assign to '[object]'". FF does, indeed, not throw an error.
This is most likely just a failing of the Firefox JavaScript engine, and in any case, does not seem to affect the functionality of the array literal [].
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Iggyhopper
Aha, fail on Firefox and on me, as I did not actually test this in another browser.