Question

I am checking if a variable is defined or not, and if it is not defined explicitly I am going to define it by doing:

if ( typeof(aVariable) == 'undefined' ) {
  var aVariable = value;
}

Because the variable is not defined JSLint warns that it is used before it is defined, and that is exactly what I want.

How can I overcome this?

I want to enable defining those variables explicitly doing this:

<script>
  var aVariable = value;
</script>
<script src="myScript.js"></script>

So everyone who is going to include this script can customize some of the properties. And I am afraid I cannot change this logic because it is already being used in hundred of web sites this way.

Scroll down for the answers/solutions, because I have answered my own question Stack Overflow does not show it up. Be sure not to miss them.

Answer 1

I found more acceptable answers in JSLint mailing list, sorry about that Boldewyn 🙂

Solution 1

In IE, at a script level (i.e. per file, or per script block), if it sees a
“var” declaration during its parse phase (before execution), it will reset the
value of that variable if it already existed.

So better would be to simply do this:

/*global foo: true */
if (typeof foo === "undefined") {
foo = "some value";
}

By not declaring “var” and simply assigning foo, foo will automatically get
global scope.

Solution 2 (special case)

If explicitly set variable is not zero or false

var foo = foo || "some value";