How to evaluate a variable to access its runtime value in JavaScript?

Question

Ok, I don't know how to actually ask this question without showing it. (Also explains why I can't figure out how to search for it on Google.)

Given the following like of code:

dijit.byId('leftNavigationPane').onLoad = function(){setSecondaryNav(url.secondaryNavId);};

I want the variable url.secondaryNavId to be evaluated, so what I really want is it to be treated something like this:

dijit.byId('leftNavigationPane').onLoad = function(){ setSecondaryNav('item1'); };

I am sure there is probably a better way to do this, so feel free to suggest something.

palswim · Accepted Answer · 2010-08-25 16:35:19Z

5

Don't use eval!

You can use a self-invoking function and closures as follows:

dijit.byId('leftNavigationPane').onLoad = function(id){
    return function(){ setSecondaryNav(id); };
}(url.secondaryNavId);

This will execute the outer anonymous function immediately (at runtime), passing the url.secondaryNavId parameter, which will then create a closure that the inner anonymous function will use (so id will always contain the assignment-time value of the url.secondaryNavId property).

edited Aug 25, 2010 at 16:35

answered Aug 19, 2010 at 18:46

palswim

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2 Comments

craineum Over a year ago

Thank You! Javascript is still a mystery to me at times.

palswim Over a year ago

Yeah, I didn't understand these as much until recently, either.

Anthony -GISCOE- · Accepted Answer · 2010-08-19 18:31:14Z

-1

There is the JavaScript eval() function.

answered Aug 19, 2010 at 18:31

Anthony -GISCOE-

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