Underscore, check if key exists in array of objects

Question

I am trying to check new data I am receiving against an object I am holding onto, and what I am trying to find out is if they key of the object I am being send matches any keys in the object I currently have.

So I am holding onto an object like

myObj = [{"one": 1}, {"two": 2 },{"three" : 3}];

And I get sent a single object like

{"three" : 5 }

And I want to just check this object against the array of objects (myObj) and see if there is anything with the key "three" inside of it ( I don't care about the values, just the key matching) so I can pop it into an if statement to separate like -

if( array of objects (myObj) has key from single object ( "three" ) ) {}

I am using underscore. Thanks!

Edit : Sorry this was not clear, I am editing it to clarify -

I am holding onto myObj (the array of objects), and being sent a single object - the "three" for example, and I just want to pull that single object key out (Object.keys(updatedObject)[0]) and check if any of the objects in the object array have that key.

So _has seems like it is just for checking a single object, not an array of objects.

possible duplicate of [Check if a key exists inside a json object](http://stackoverflow.com/questions/20804163/check-if-a-key-exists-inside-a-json-object) — Sergiu Paraschiv, Mar 03 '15 at 15:38
Google "javascript check if key exists in object" returns three relevant results. — Sergiu Paraschiv, Mar 03 '15 at 15:38
@SergiuParaschiv: not a duplicate at all. Its `underscore.js` — naveen, Mar 03 '15 at 15:40
Not a duplicate, this regards using underscore, maybe we should remove the javascript tag to avoid confusion — Dexygen, Mar 03 '15 at 15:44
The only reason anyone would use anything other than hasOwnProperty would be browser support, right? — Sergiu Paraschiv, Mar 03 '15 at 17:32

score 13 · Accepted Answer · answered Mar 03 '15 at 16:37

13

You're looking for the _.some iterator combined with a callback that uses _.has:

if (_.some(myObj, function(o) { return _.has(o, "three"); })) {
    …
}

answered Mar 03 '15 at 16:37

Bergi

630,263
148
957
1,375

score 10 · Answer 2 · answered Mar 03 '15 at 15:39

10

You can use underscore method 'has'

Here the example:

_.has({"three" : 5 }, "three");
=> true

From the underscore doc:

Does the object contain the given key? Identical to object.hasOwnProperty(key), but uses a safe reference to the hasOwnProperty function, in case it's been overridden accidentally.

answered Mar 03 '15 at 15:39

Sergiy Kozachenko

1,399
11
31

This is on the right track - however it is not checking if the array of objects has "three". – ajmajmajma Mar 03 '15 at 16:10

Underscore, check if key exists in array of objects

2 Answers2