If not declared, declare the variable?

Question

The topic might be a bit cryptic, but here's my problem (perhaps a n00b-thing?):

For my site I have a widget, that user can use on their site as such (for example):

<script type="text/javascript">
    var widget_width ="300";
</script>
<script src="http://something/a.js" type="text/javascript"></script>

Now, in the .js file I want to check if the user have declared the widget_width variable. So I thought I might do something like (I want the variable to be empty, "", because I do a server-side validation too):

if(typeof widget_width == 'undefined') {
    var widget_width = "";
}

This didn't work, neither did:

if(!widget_width) {
    var widget_width = "";
} 

Any ideas on how do declare a variable when needed this way?

Answer 1

remove the var. make it >

if(typeof widget_width == 'undefined') {
    widget_width = "";
}