Set a variable variable on an object in javascript

Question

Doing some work with Omniture analytics and want to be able to set some properties via JSON.

Omniture calls look something like this:

s.linkTrackVars = 'eVar37';
s.eVar37='foo';
s.tl(true, 'o');

I want to write a generic function to take a JSON object and convert it into those variables. AFAIK Omniture doesn't allow you to simply pass it JSON, so this the only method I can think of.

Here's the example of the JSON structure I want to use:

var omniture = {

    "evars":
    [
        {
            "key": "37",
            "value": "foo"
        },

        {
            "key": "32",
            "value": "bar"
        }
    ]

}

My function to work with this JSON looks like this:

for (i in omniture.evars) {
    var evar = omniture.evars[i];
    window[s.eVar + evar.key] = evar.value;
}
alert(s.eVar37); // alerts "undefined"

If I do this, it works:

for (i in omniture.evars) {
    var evar = omniture.evars[i];
    window['eVar' + evar.key] = evar.value;
}
alert(eVar37); // alerts "foo"

It seems that I can't set a variable variable as a property of an object (eg s.eVar37 as opposed to evar37). Can anybody think of a nice way of setting these variables automatically?

thanks, Matt

There is no JSON in your example, it's a plain JS object.

Felix Kling
– Felix Kling

2011-05-27 11:41:28 +00:00
Commented May 27, 2011 at 11:41 — Felix Kling
– Felix Kling, Commented May 27, 2011 at 11:41

Samir Talwar · Accepted Answer · 2011-05-27 11:40:48Z

3

Sure you can. Just set it on s directly:

s['eVar' + evar.key] = evar.value;

answered May 27, 2011 at 11:40

Samir Talwar

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1 Comment

Matt Andrews Over a year ago

Oh... doh! As simple as that. Thank you.

entonio · Accepted Answer · 2011-05-27 11:52:09Z

1

IIUC you want s['eVar' + evar.key] = evar.value;.

edit: alternative

It would be simpler though to just have

var omniture =
{
    evars:
    {
        "37": "foo",
        "32": "bar"
    }
}

copyFromInto(omniture.evars, 'eVar', s);

function copyFromInto(o1, prefix, o2)
{
    for (var i in o1)
    {
         o2[prefix + i] = o1[i];
    }
}

alert(s.eVar37); // alerts "foo"

But of course it all depends on what you want to do.

edited May 27, 2011 at 11:52

answered May 27, 2011 at 11:42

entonio

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