CODEWITHSUNDEEP
javascript
ehime
ehime

Reputation: 8375

Javascript variable or new function causing errors in IE

Hey guys I'm having an issue with this statement in Internet Explorer, I was wondering if there is a saner way to do it?

var NEWVARIABLE = NEWVARIABLE || {};
NEWVARIABLE.Tools = NEWVARIABLE.Tools || {};

Its giving me the error that NEWVARIABLE does not exist

Upvotes: 0

Views: 168

Answers (2)

Ruan Mendes
Ruan Mendes

Reputation: 92274

You cannot use (or test) a variable that's not been defined. I originally thought that's what you were doing with the following statement

var NEWVARIABLE = NEWVARIABLE || {};

However, thanks to Fabrício, I realized that the var declaration gets hoisted (moved to the top of the script tag and is therefore already declared when it hits the statement.

The less confusing way to test if a variable is to use typeof === 'undefined' to see if a variable exists

var NEWVARIABLE;
if (typeof NEWVARIABLE === 'undefined') {
    NEWVARIABLE = {};
}

You can use the same style when checking for properties, you don't have to use typeof test for properties, you are allowed to test them even if they aren't defined.

Upvotes: 3

RobG
RobG

Reputation: 147363

You've accepted an answer, but it contains a misleading statement:

You cannot use (or test) a variable that's not been defined. That's what you're doing

The variable is declared, so it isn't what you are doing.

In the OP, the code:

> var NEWVARIABLE = NEWVARIABLE || {};
> NEWVARIABLE.Tools = NEWVARIABLE.Tools || {};

contains no syntax errors, the only case where it will throw an error is if NEWVARIABLE already exists and has a Tools property that throws an error when attempting to access or assign to it (as may happen with certain host objects).

If NEWVARIABLE has previously been assigned a native object or primitive value, it will not throw an error, though the result may not be what you expect.

Upvotes: 0

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