find the array index of an object with a specific key value in underscore

In underscore, I can successfully find an item with a specific key value

var tv = [{id:1},{id:2}]
var voteID = 2;
var data = _.find(tv, function(voteItem){ return voteItem.id == voteID; });
//data = { id: 2 }

but how do I find what array index that object occurred at?

findIndex was added in 1.8:

index = _.findIndex(tv, function(voteItem) { return voteItem.id == voteID })

See: http://underscorejs.org/#findIndex

Alternatively, this also works, if you don't mind making another temporary list:

index = _.indexOf(_.pluck(tv, 'id'), voteId);

See: http://underscorejs.org/#pluck

Lo-Dash, which extends Underscore, has findIndex method, that can find the index of a given instance, or by a given predicate, or according to the properties of a given object.

In your case, I would do:

var index = _.findIndex(tv, { id: voteID });

Give it a try.