Get key using value from an object in JavaScript?

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,
            "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?


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

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

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];



Try findKey() lodash method:

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

where val - property value.

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