How can i concatenate var names to declare new vars in javascript?:

var foo = 'var';
var bar = 'Name';

How can i declare variable varName?

How can i concatenate var names to declare new vars in javascript?:

var foo = 'var';
var bar = 'Name';

How can i declare variable varName?

• javascript

Share Improve this question Follow edited May 28, 2009 at 3:04 Daniel Magliola 32.5k6363 gold badges174174 silver badges246246 bronze badges asked May 28, 2009 at 2:56 BabikerBabiker 18.8k2828 gold badges8282 silver badges127127 bronze badges 3

• 3 Just out of curiosity, why would you need to do that? Chances are, you're doing something wrong. – Sasha Chedygov Commented May 28, 2009 at 3:06
• It make Javascript harder to read because you can't search where declare variable by using simple search like this("var [variable name]"). – user94893 Commented May 28, 2009 at 3:35
• 1 I have pre-declared var names that the user might be invoke based on user text input. – Babiker Commented May 28, 2009 at 3:40

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5 Answers 5

Sorted by: Reset to default 12

Try something like:

window[foo + bar] = "whatever"; 
alert(varName);

do not use the eval function unless you are absolutely certain about what's going in. window[] is much safer if all you're doing is variable access

To dynamically declare a local variable (i.e. var fooName), I guess you could use eval:

eval('var ' + foo + bar);

Best to avoid eval though, if you can avoid it (see related question).

A better way is to set an object property. Defining a global variable is equivalent to setting a property on the global object window:

window[foo+bar] = 'someVal';

You can substitute window for another object if appropriate.

WARNING: VaporCode! Off the top of my head...

window[foo + bar] = "contents of variable varName";

Does that work?

Locally:

this[foo+bar] = true;

Globally:

window[foo+bar] = true;

there may be a better way but eval should do it

eval('var ' + foo + bar);