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.

possible duplicate of http://stackoverflow.com/questions/12167800/using-eval-to-set-global-variables — Will P., Feb 18 '14 at 22:49
As stated above; do `obj[variableNames[i]] = variableValues[i];` — Johan, Feb 18 '14 at 22:50
some explanation: http://stackoverflow.com/questions/5117127/javascript-dynamic-variable-name — MamaWalter, Feb 18 '14 at 22:50
@WillP. There is no reason to settle with a solution just because it works. Polluting the global namespace is known as a bad practice — Johan, Feb 18 '14 at 22:55

score 1 · Accepted Answer · answered Feb 18 '14 at 22:53

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"

loxxy · Answer 2 · 2014-02-18T23:03:15.130

0

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.

edited Feb 18 '14 at 23:03

answered Feb 18 '14 at 22:55

loxxy

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Someone had to highlight the error. Maybe OP is just curious, or perhaps a reason for doing so. :) – loxxy Feb 18 '14 at 22:59

Defining variables dynamically in Javascript

2 Answers2