How can I check the variable whether it exists or not

Question

var a;
typeof(a);
//undefined

typeof(c);
//undefined

if(c) {}
//throw error

How can I know that c doesn't exist without try catch.

Update after marked duplicate:
typeof initializedVariable and typeof notInitializedVariable both will show 'undefined'. My question is to know whether the variable exists(initialized) or not.

What was the problem with the other similar questions (see list at right, you should have seen it when making the question) ? — Denys Séguret, Jul 09 '13 at 09:25
Why don't you want a warning if you try to use a variable that doesn't exist? — 1983, Jul 09 '13 at 10:01
`typeof initializedVariable` and `typeof notInitializedVariable` both will show 'undefined'. My question is to know whether the variable exists(initialized) or not. — vusan, Oct 12 '17 at 10:42

score 3 · Accepted Answer · answered Jul 09 '13 at 09:25

3

You can use the typeof operator.

 if (typeof a === 'undefined') {
     // variable is undefined
 }

answered Jul 09 '13 at 09:25

AllTooSir

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That doesn't address the question (it is a bad q. though). – 1983 Jul 09 '13 at 10:00
`typeof c === 'undefined'` is also `true`. – vusan Oct 12 '17 at 10:34

How can I check the variable whether it exists or not

1 Answers1