Angularjs: Inject underscore into $scope

Question

I am having a weird problem with not being able to use underscore functions inside either the {{}} or inside the ng-repeat and other expressions. My exact test function was

{{_.last([1,2,3,4])}}

... right in the HTML of the page.

I am able to see the correct answer (4) only if I do this in my controller:

$scope._ = _;

I tried to inject _ as a factory into my main application module and then inject that into my controller, but it doen't seem to inject it into the $scope.

Can anyone see the mistake I am making? Or is there a mechanism there that would prevent the underscore library from getting into the $scope? I am using angular v.1.0.7 and a recent version of underscore (not sure of the exact version number, but it is within the last 3 weeks).

To clarify, I can use underscore fine inside the controller itself. It is only not "visible" in the view (inside of the HTML markup). — electrichead
– electrichead, Commented Jun 28, 2013 at 14:10
To anyone reading this in 2015: Please don't do this! Write a function in your controller and use underscore/Ramda/lodash etc. there instead. Injecting these libraries into your view bypasses the safeguards in expressions and is generally a bad idea! — electrichead
– electrichead, Commented Sep 2, 2015 at 17:21

Stewie · Accepted Answer · 2013-06-28 14:14:43Z

5

Angular expressions ({{expression}}) are evaluated against the local $scope, which, in case you have defined a controller, is a $scope object as in function MyCtrl($scope){}.

So, when you use _ in your expressions, the _is evaluated against the $scope, and since $scope.doesn't have a _ member, you expression fails.

So, the only to use _in your views is to make it available on $scope object with: $scope._ = _;.

Btw, when used in browser context, underscore adds _as global object, so it's available throughout your JS. This means that there's no need to "inject _as a factory".

answered Jun 28, 2013 at 14:14

Stewie

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1 Comment

electrichead Over a year ago

I was trying the injection because of this thread ( stackoverflow.com/questions/14968297/… ), but it turns out that was to make it available in the controller. Ironically, the answer to my question was in the OP's question, not in the answer I found through the google search. I am now injecting underscore into the $rootScope when the application loads. Thanks for clarifying!

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