JavaScript in operational throw a exception?

Question

code like this

<script type="text/javascript">
  var name = [2,3,4];
  var a = (1 in name);
  console.log(a);
</script>

but throw error

if code like this:

<script type="text/javascript">
  var names = [2,3,4];
  var a = (1 in names);
  console.log(a);
</script>

no error! why? test on firefox!

name ... is actually `window.name` which is always a string and can't be changed from a string — Jaromanda X, Dec 01 '15 at 13:29
@JaromandaX: That's an answer. :-) We've had this question a couple of dozen times, but it's **really** hard to find originals to use as close-targets... — T.J. Crowder, Dec 01 '15 at 13:30
@T.J.Crowder - I'm sure I learned that here on SO - looking for the dupe :D — Jaromanda X, Dec 01 '15 at 13:31
@Abhitalks: Nope, fails in Chrome too. The key here is that the code must be at global scope. If it's inside a function (like jsFiddle's default `onload` handler), it'll work as-is. — T.J. Crowder, Dec 01 '15 at 13:32
@Abhitalks ... the **first** code snippet doesn't work, the **second* does ... it's the same in firefox and chrome at least ... if you think the first code works, you did it wrong — Jaromanda X, Dec 01 '15 at 13:32
@T.J.Crowder nope it does not fail in chrome if you use variable named as 'names' instead of 'name' — Viraj Nalawade, Dec 01 '15 at 13:33
that's exactly what the question says ... `name` fails, `names` works — Jaromanda X, Dec 01 '15 at 13:34
@T.J.Crowder: I've just used one. If you find a better (earlier?) duplicate target, let me know :-) — Bergi, Dec 01 '15 at 13:37
@T.J.Crowder: In fact I've looked closer now and there are [many more](https://stackoverflow.com/search?q=window.name+string). The [earliest occurence](http://stackoverflow.com/q/10523701/1048572) seems to be from May '12, and is answered quite well (if a bit short maybe). What do you think, should we use it as a canonical target or are there better ones? — Bergi, Dec 01 '15 at 13:56

score -1 · Answer 1 · answered Dec 01 '15 at 13:33

-1

Since there is a possibility of scope issues with the variable name, do create a scope with something like this:

(function() {
  var name = [2,3,4];
  var a = (1 in name);
  console.log(a);
})();

answered Dec 01 '15 at 13:33

Candide

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JavaScript in operational throw a exception?

1 Answers1