find updated field in object - scope.$watch - angularjs

Question

If i do:

scope.$watch('obj', function(newObj, oldObj) {
  //...
}, true);

How do I find the key-value pair in the object that changed?

.

Only to understand what I try to do:

I have an object of the form:

scope.actions = {
  action1: false,
  action2: false
}

When the boolean changes, I want to assign function calls to it. Something like, DO-action - UNDO-action.

So I watch it the following way:

scope.$watch('actions', function(newObj, oldObj) {

  /*PSEUDO CODE START*/

  IF (action1 changed && action1 true) {
    do-func1();
  }
  IF (action1 changed && action1 false) {
    undo-func1();
  }
  ...
  /*PSEUDO CODE END*/

}, true);

My problem here is, that if I check the values for their boolean, all the functions get called. So the point here is, how do I find the changed key-value pair in the object?

Do you have only 2 actions, or there might be arbitrary number of actions? — sbedulin
– sbedulin, Commented Jun 19, 2015 at 14:11

sbedulin · Accepted Answer · 2015-06-19 14:30:25Z

1

scope.$watch('actions', function(newActions, oldActions) {
    for(var i in newActions) {
        if(newActions.hasOwnProperty(i)) {
            var newAction = newActions[i];
            var oldAction = oldActions[i];

            if(newAction !== oldAction) {
                if(newAction === true) {
                    doActions[i](); // do-func-i();
                } else if (newAction === false) {
                    undoActions[i](); // undo-func-i();
                }
            }
        }
    }
}, true);

doActions here is a conventional map of actions

doActions = {
    action1 : function() {
        console.log('action1');
    },
    action2 : function() {
        console.log('action2');
    }
}

doActions['action1'] will reference first function

You may have an array as well, but then you'll need to introduce an index to fetch proper function doActions[0]

edited Jun 19, 2015 at 14:30

answered Jun 19, 2015 at 14:20

sbedulin

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