How to avoid updating original array after using $filter?

Question

Please see below code:

var fieldsControls = $filter('filter')(vm.FieldsControls, { FieldId: id });

            for (var i = 0; i < fieldsControls.length; i++)
            {
                if (fieldsControls[i].ControlType == "DropDown") {
                    fieldsControls[i].Options = $filter('filter')(vm.Options, { type: fieldsControls[i].type });
                }
            }
            return fieldsControls;

After return (or even after the for loop) I observed that the original array "vm.FieldsControls" is getting updated with new Options value. However, shouldn't this just change new array fieldControls only?

Przemek · Accepted Answer · 2016-02-11 16:13:49Z

2

Prepare deep copy of you array first. Here is the code:

     var copy = angular.copy(vm.FieldsControls);

     var fieldsControls = $filter('filter')(copy, { FieldId: id });

        for (var i = 0; i < fieldsControls.length; i++)
        {
            if (fieldsControls[i].ControlType == "DropDown") {
                fieldsControls[i].Options = $filter('filter')(vm.Options, { type: fieldsControls[i].type });
            }
        }
        return fieldsControls;

edited Feb 11, 2016 at 16:13

answered Feb 11, 2016 at 15:25

Przemek

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2 Comments

TechTurtle Over a year ago

I tried it, but it gives error as "fieldsControls is undefined".

Przemek Over a year ago

Sorry, I used old syntax. this is as it should be: var copy = angular.copy(vm.FieldsControls); @TechTurtle

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