Object assignment does not work in this angularjs controller

Question

Inside my angularjs controller, I try to assign an object into a $scope.XX object. For some reason, it cannot work. Here is a simplified version of the code inside the angularjs controller.

    $scope.XXX = {};
    polling_interval_ms = 100;          

    var poll = function (ChartObj, polling_interval_ms) {
        var processedObj = {};
        processedObj = processDataChart(data_Chart); //data_Chart is object that contains data that changes in real-time
        ChartObj = Object.assign(processedObj);
        console.log(ChartObj);

        $timeout(function () {
            poll(ChartObj, polling_interval_ms)
        }, polling_interval_ms);
    };

    poll($scope.XXX, polling_interval_ms);
    console.log($scope.XXX);

The strange part is the output of console.log(ChartObj); shows that data has been assigned to the object. However, the output of console.log($scope.XXX) is empty. I was expecting $scope.XXX to contain same data as ChartObj. What did I do wrong?

Grundy · Accepted Answer · 2016-03-25 07:55:05Z

1

In javascript all parameters in function is reference. So when you change reference - you not change referenced object.

In your case you can use Object.assgin in a bit different way

Object.assign(ChartObj, processedObj);

because

The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.

Or pass wrapper for object XXX, in this case it a $scope

$scope.ChartObj = {};
polling_interval_ms = 100;          

var poll = function (wrapper, polling_interval_ms) {
    var processedObj = {};
    processedObj = processDataChart(data_Chart); //data_Chart is object that contains data that changes in real-time
    wrapper.ChartObj = Object.assign(processedObj);
    console.log(wrapper.ChartObj);

    $timeout(function () {
        poll(wrapper, polling_interval_ms)
    }, polling_interval_ms);
};

poll($scope, polling_interval_ms);
console.log($scope.ChartObj);

edited Mar 25, 2016 at 7:55

answered Mar 25, 2016 at 7:49

Grundy

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2 Comments

guagay_wk Over a year ago

Wonderful. I wish I can given you more points. Wonderful!!! I spent hours while you took minutes. You are a genius!!

Grundy Over a year ago

@user16891328, just be more attentive when reading the documentation for the function :-)

Grundy · Accepted Answer · 2016-03-25 07:41:15Z

1

Use

$scope.XXX

instead of ChartObj because

your are assigning value to

ChartObj

and

$scope.XXX

is not a refrence type

edited Mar 25, 2016 at 7:41

Grundy

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answered Mar 25, 2016 at 7:38

Hassan Tariq

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