Return name of object property by value in Javascript?

Question

I have a javascript object that maps ids:

codes = { 
    "admin" : 3,
    "manager" : 2,
    "basic" : 1
}

Given a value...

accountType = 2;

...what is the most elegant way to find the corresponding key ("manager") ?

What should happen with an object like {admin:2, manager:2}? — Bergi
– Bergi, Commented Mar 16, 2013 at 20:30
For mapping db values to something more readable. (I'm not interested in using a join table for this.) — user1031947
– user1031947, Commented Mar 16, 2013 at 20:34

gdoron · Accepted Answer · 2013-03-16 20:11:21Z

3

for (var i in codes){
    if (codes[i] == accountType)
        alert(i);
}

Live DEMO

jQuery version, though there is really no benefit from using it here:

$.each(codes, function(key, value){
        if (value == accountType)
            alert(key);
});

Live DEMO

edited Mar 16, 2013 at 20:11

answered Mar 16, 2013 at 20:01

gdoron

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3 Comments

user1031947 Over a year ago

Thanks - I was wondering if there might be a way to do this without manually iterating through the properties

gdoron Over a year ago

@user1031947, I'm afraid not. Sorry.

gdoron Over a year ago

@user1031947, but if the object key value pairs were like: codes = { "3" : "admin", "2" : "manager", "1" : "basic" } you could have used this: codes["2"]

Guffa · Accepted Answer · 2013-03-16 20:17:52Z

1

If you do this a lot, it would be efficient to keep an object to use for the reverse lookup:

codeNames = { 
  "3": "admin",
  "2": "manager",
  "1": "basic"
}

Now you can just access the properties by name:

var name = codeNames[accountType];

You can create the lookup object from the codes object:

var codeNames = {};
for (var i in codes){
  codeNames[codes[i]] = i;
}

answered Mar 16, 2013 at 20:17

Guffa

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1 Comment

gdoron Over a year ago

+1, though I think it's awful to have two objects to two different lookups. It can cause more pain than gain.

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