Defining variables dynamically in Javascript

Question

In a situation where I have something like this code:

var variableNames=["thisMonth", "thisDay"];
var variableValues=["February", 17];

Is there any way I could go through the array and initiate variables with their corresponding values? I've tried something like

for(var i=0;i<variableNames.length;i++){
 eval("var "+variableNames[i]+"="+variableValues[i]+";");
}

But I'm not getting any reults. Is eval not able to define variables, or are there other problems that exist? Any solution would be greatly appreciated.

• Dave Newton: Why would you want to? Use an object.
• Will P.: possible duplicate of stackoverflow.com/questions/12167800/…
• Johan: As stated above; do obj[variableNames[i]] = variableValues[i];
• MamaWalter: some explanation: stackoverflow.com/questions/5117127/…
• Will P.: @Johan, correct, and that obj could be window

Answer 1

You need to assign the variables on an object. If you want to create global variables the following code should work:

for (var i=0; i<variableNames.length; i++) {
 window[variableNames[i]] = variableValues[i];
}
//test
console.log(thisMonth); //"February" 

Answer 2

Here you go. You missed a couple of quotes at "='" + variableValues[i] + "';");:

var variableNames=["thisMonth", "thisDay"];
var variableValues=["February", 17];
for(var i=0;i<variableNames.length;i++){
 eval("var "+variableNames[i]+"='"+variableValues[i]+"';");
}

With that correction however, I would warn you against using it cause it's a very wrong way of doing it.

Use Objects, as most here mention.

• loxxy: Someone had to highlight the error. Maybe OP is just curious, or perhaps a reason for doing so. :)