Check if an element is in an array

Question

I have a JS array of objects like this:

Ident: "2"
Text: "Foo"

Now I want to check if the object with the Ident equal to 2 is in the array. How can I do this? It's not possible with jQuery.inArray because I don't have the whole object, just the Ident.

A regular loop should work fine. If you check the values a lot it makes sense to create a new object (with the data as keys) to cache it (see this jsperf). What have you tried? — h2ooooooo
– h2ooooooo, Commented May 26, 2014 at 14:23
Are you working with an array of objects? Or with an object that serves as associate array? — Victor
– Victor, Commented May 26, 2014 at 14:26
There's a find function in ES6 and it's supported by some browsers. A polyfill is available. — Pointy
– Pointy, Commented May 26, 2014 at 14:26

lonesomeday · Accepted Answer · 2014-05-26 14:29:51Z

3

You will indeed have to do the loop the long way here:

function findByIdent(array, ident) {
    var i;

    for (i = 0; i < array.length; i++) {
        if (array[i].Ident === ident) {
            return i;
        }
    }

    return -1; // not found
}

If it's any consolation, this used to be the way all is-this-element-in-this-array calls were done!

Note that this presumes that you have an array that looks approximately like this:

[{Ident: "2", Text: "foo"}, {Ident: "3", Text: "bar"}]

answered May 26, 2014 at 14:29

lonesomeday

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Serg Tomcat · Accepted Answer · 2014-05-26 14:30:53Z

3

As you had mentioned JQuery, you can use "grep" method:

 if (jQuery.grep(arr, function( n ) {
   return ( n.Ident == "2" );
 }).length)
 ...

but it will loop through all elements.

answered May 26, 2014 at 14:30

Serg Tomcat

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1 Comment

lonesomeday Over a year ago

Yes, if you're looking for true/false rather than the index, that's a nice solution.

serakfalcon · Accepted Answer · 2014-05-26 14:33:07Z

1

var found = false;
for (var i =0;i<somearray.length;i++) {
    if (somearray[i].Ident === 2) {
        found = true;
        break;
    }
}

answered May 26, 2014 at 14:33

serakfalcon

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