How can i concatenate var names to declare new vars in javascript?:
var foo = 'var';
var bar = 'Name';
How can i declare variable varName?
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3Just out of curiosity, why would you need to do that? Chances are, you're doing something wrong.Sasha Chedygov– Sasha Chedygov2009-05-28 03:06:49 +00:00Commented May 28, 2009 at 3:06
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It make Javascript harder to read because you can't search where declare variable by using simple search like this("var [variable name]").user94893– user948932009-05-28 03:35:00 +00:00Commented May 28, 2009 at 3:35
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1I have pre-declared var names that the user might be invoke based on user text input.Babiker– Babiker2009-05-28 03:40:48 +00:00Commented May 28, 2009 at 3:40
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5 Answers
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
1 Comment
olliej
An additional reason to not use eval is that strict mode ECMAScript 5 does not allow eval to inject new variables
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.
Comments
WARNING: VaporCode! Off the top of my head...
window[foo + bar] = "contents of variable varName";
Does that work?
1 Comment
Babiker
how can i go about the problem?
Locally:
this[foo+bar] = true;
Globally:
window[foo+bar] = true;
Comments
there may be a better way but eval should do it
eval('var ' + foo + bar);
1 Comment
Daniel Magliola
@Babiker: Eval really is a bad practice, and dangerous, especially considering your comment about using user input to define what variable you'll be using. Not that anything a user can do in JS can be dangerous if your server is secure anyway, but still... using window[foo+bar] is definitely safer.