Javascript variable is undefined outside if condition

Question

I have defined a javascript variable but it returns undefined.

variable = "";

if(somecondition){
      variable=myString.length;
}
alert(variable);

here variable returns undefined. If I keep the alert inside the if condition, I am able to get the value but its not working if I keep the alert outside the if condition.

you missed adding var to it..did you define myString correctly...try adding var and check — Geeky, Oct 14 '16 at 17:56
@NongthonbamTonthoi I have tried using var variable also. But the result is the same. — SRM, Oct 14 '16 at 17:56
Can you show what is myString and what exactly is your condition — Geeky, Oct 14 '16 at 17:58
Please make an example that illustrates your exact problem. [I threw this together](https://jsfiddle.net/gap4xbhL/) (making some simple assumptions) and your code works as you would expect it to. — Mike Cluck, Oct 14 '16 at 18:00
myString is not defined , define it outside as var myString =[] — nivendha, Oct 14 '16 at 18:01
@nive32 `myString` is defined, but it hasn't `length` property. If it wasn't defined, there would occur an error, and the alert would never be executed. — Teemu, Oct 14 '16 at 18:02
@Teemu , yes i agree, that should be the one assigning the undefined value — nivendha, Oct 14 '16 at 18:04

Panther · Answer 1 · 2016-10-14T19:21:50.917

1

Your myString does not have an property called length and hence you are getting undefined. Usually, String, array has length property while objects don't have it.

Either you are invoking a wrong property or invoking it on a wrong data type or you have to define one yourself :P

edited Oct 14 '16 at 19:21

answered Oct 14 '16 at 18:04

Panther

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That's what I said! – Andrew Vogel Oct 14 '16 at 20:25

score 0 · Answer 2 · answered Oct 14 '16 at 17:56

0

Using var will do it:

var variable;

answered Oct 14 '16 at 17:56

Luiz Chagas Jr

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score 0 · Answer 3 · answered Oct 14 '16 at 17:57

0

You need to declare and define your variable.

var variable = "";

if(somecondition) {
      variable = myString.length;
}

alert(variable);

answered Oct 14 '16 at 17:57

James Monger

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No. `var` isn't necessary, since all of the code is in the SAME scope. – Marc B Oct 14 '16 at 17:59
3

^ although you should definitely declare your variables with `var` (or some other declaration keyword) to avoid making globals. – Mike Cluck Oct 14 '16 at 18:01

Nongthonbam Tonthoi · Answer 4 · 2016-10-14T18:02:33.817

0

var variable = '';
if (true) {
     variable = 'Yes'
}
alert(variable);

This will show alert as Yes.

So in your case myString.length; is probably undefined

edited Oct 14 '16 at 18:02

answered Oct 14 '16 at 18:00

Nongthonbam Tonthoi

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But I am able to see the vlue if I alert inside the if condition which means there is no problem with the string. – SRM Oct 14 '16 at 18:02
Which value can you see inside the if condition? The .length value? What is it? – Andrew Vogel Oct 14 '16 at 20:29

score 0 · Answer 5 · answered Oct 14 '16 at 18:02

0

Are you missing the initialization of mystring?

Look at the following

answered Oct 14 '16 at 18:02

Pandiyan Cool

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No. I have initialized the string in the same way. and I amble to see the value inside the condition – SRM Oct 14 '16 at 18:03
may be your condition is not valid or your mystring variable doesn't have length property – Pandiyan Cool Oct 14 '16 at 18:07

Andrew Vogel · Answer 6 · 2016-10-14T20:24:58.440

-1

If variable isn't undefined in the function, it's because it is still equal to the initial value, "" (Empty String).

What I bet is happening, is myString is actually a number and not a string. Try the following and see if you are still having a problem:

variable = "";

if(somecondition){
      variable=myString.toString().length;
}
alert(variable);

edited Oct 14 '16 at 20:24

answered Oct 14 '16 at 18:06

Andrew Vogel

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Javascript variable is undefined outside if condition

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