Understanding $watch in AngularJS?

Question

I am a little confused with the $watch syntax in AngularJS.

Given a variable $scope.foo, with initial value of [1,2,3], and update causes it to now equal [1,2]. I want a function to be run whenever $scope.foo is updated, with $scope.foo as arg.

How do I do this in AngularJS?

Solution

That's pretty simple:

function myFunction(foo) {
    // do something with `foo`
}

$scope.$watch('foo', function(newValue, oldValue) { 
    myFunction(newValue);
});

More details are found in the AngularJS documentation about $watch.

Comments

[TidharPeer]

You can add the $ sign before the 'scope'

[Moritz Petersen]

@TidharPeer You're right, done that.

[Foo Stack]

Thanks, but I can't seem to get it to work with $http, here's what I've tried.