How do i check if a few variables are defined?

Question

ich want to check if my 3 variables are defined but this doesnt work:

If (typeof inputServer && inputUser && inputPassword !="undefined") {
        alert("it works!");
    }

My debugger says "Uncaught SyntaxError: Unexpected token { "

Please help me :)

greets Tom

score 4 · Answer 1 · edited May 23 '17 at 12:04

4

JavaScript is case sensitive language. if keyword starts with small i.

Additionally, I'd recommend you to use typeof inputServer !== "undefined" to check if variable was defined.

REF: Detecting an undefined object property

edited May 23 '17 at 12:04

Community

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answered Apr 16 '13 at 17:12

VisioN

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I would not. Really, who is stupid enough to define undefined? – jgillich Apr 16 '13 at 17:19
@jgillich It's fool-proof solution anyway. – VisioN Apr 16 '13 at 17:20
1

Sometimes it is better to learn things the hard way. But that's just my humble opinion. :) – jgillich Apr 16 '13 at 17:23
I agree with @jgillich. The clunky `typeof foo !== "undefined"` syntax causes more errors *(due to typing it incorrectly)* than actually redefining `undefined`. – Apr 16 '13 at 17:32

score 3 · Answer 2 · answered Apr 16 '13 at 17:13

3

if ((inputServer != undefined) && (inputUser != undefined) && (inputPassword != undefined)) {
        alert("it works!");
}

answered Apr 16 '13 at 17:13

zavg

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score 0 · Answer 3 · answered Apr 16 '13 at 17:14

it's if(all lower) and not If - and if the vars is not defined it's still gives you an error cause you are asking them - what you can do is (assuming this code runs at global scope as i understand:

if(typeof(window.inputServer) != 'undefined' && typeof(window.inputUser) != 'undefined'){

}

holographic-principle · Accepted Answer · 2013-04-16T17:58:48.943

First, if should be lowercase.

Then, you could do it like this:

if (inputServer !== undefined && inputUser !== undefined && inputPassword !== undefined) {
    alert("it works!");
}

If you wanted to check if they were not undefined OR null you could do (and this is one of the rare circumstances when using double equality is useful):

if (inputServer != null && inputUser != null && inputPassword != null) {
    alert("it works!");
}

And lastly, if you wanted to check if they weren't any falsy value (null, undefined, false, -0, +0, NaN, ''), you could do:

if (inputServer && inputUser && inputPassword) {
    alert("it works!");
}

Sidenote: You don't need to use typeof in most normal circumstances -- that is unless undefined is actually a variable defined somewhere in your program...

Fortunately, in ECMAScript 5.1 it's not possible to overwrite window.undefined http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.1.3

How do i check if a few variables are defined?

4 Answers4