Get key using value from an object in JavaScript?

Question

c =      {
            "UNKNOWN_ERR" : 0,
            "INDEX_SIZE_ERR" : 1,
            "DOMSTRING_SIZE_ERR" : 2,
            "HIERARCHY_REQUEST_ERR" : 3,
            "WRONG_DOCUMENT_ERR" : 4,
            "INVALID_CHARACTER_ERR" : 5,
            "NO_DATA_ALLOWED_ERR" : 6,
            "NO_MODIFICATION_ALLOWED_ERR" : 7,
            "NOT_FOUND_ERR" : 8,
            "NOT_SUPPORTED_ERR" : 9}

To get the value using the key is easy, I just use the key in c["UNKNOWN_ERR"] to get 0, given that all the values are unique is safe to get the key (message) from the value(errorcode).

Is there a standard way to do that or do I need to write a function that looks in all key and search that specific value?

Possible duplicate of best way to get the key of a key/value javascript object — Andrei
– Andrei, Commented Feb 4, 2016 at 18:03
Probably a duplicate of stackoverflow.com/questions/9907419/… — user6913790
– user6913790, Commented Jul 4, 2019 at 10:29

ThiefMaster · Accepted Answer · 2012-11-07 16:38:24Z

18

As you already assumed you need to iterate over the object's attributes and check the value.

for(var key in c) {
    if(c[key] === whatever) {
        // do stuff with key
    }
}

answered Nov 7, 2012 at 16:38

ThiefMaster

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Comments

Fareed Alnamrouti · Accepted Answer · 2017-01-10 11:35:12Z

13

es6 find method:

const getKey = (obj,val) => Object.keys(obj).find(key => obj[key] === val);

in your case

console.log(getKey(c,1)); // INDEX_SIZE_ERR

answered Jan 10, 2017 at 11:35

Fareed Alnamrouti

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1 Comment

Non404 Over a year ago

This doesn't work when the value is 0

Pratik · Accepted Answer · 2014-01-24 11:22:05Z

6

Underscore provides a more easy solution to this

You can get key using this code also

var errKey = _.invert(c)[errCode];

for e.x. if you use errCode = 3 as shown below

var errKey = _.invert(c)[3];

then

errKey will be HIERARCHY_REQUEST_ERR

answered Jan 24, 2014 at 11:22

Pratik

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Comments

ns16 · Accepted Answer · 2019-03-27 16:03:42Z

2

Try findKey() lodash method:

var key = _.findKey(c, v => v === val)

where val - property value.

edited Mar 27, 2019 at 16:03

answered Nov 21, 2017 at 13:00

ns16

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1 Comment

Matteo Over a year ago

The original question does not seem to ask about external libraries.

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