Watching a specific member in objects of an array in angularjs

Question

I have an array of objects, something like:

$scope.arr = [{firstName: 'foo', lastName: 'bar'}, {firstName: 'john', lastName: 'doe'}]

I want to use $scope.$watch to watch only the firstName member in the array items. Something like $scope.$watch('arr[*].firstName', ... ) . Is it possible?

Thanks!

JB Nizet · Accepted Answer · 2013-12-15 09:58:38Z

1

you could simply have the following function in your scope:

$scope.getFirstNames = function() {
    return $scope.arr.map(function(element) {
        return element.firstName;
    });
}

And then use

$scope.$watch('getFirstNames()', ...

answered Dec 15, 2013 at 9:58

JB Nizet

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2 Comments

musically_ut Over a year ago

I suspect that this will actually trigger the watcher every $digest loop since the .map will produce a new array reference every time.

JB Nizet Over a year ago

Not if the third argument to $watch (objectEquality) is set to true

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