AngularJS $watch, wait variable declaration to trigger

Question

I have the below code :

variable declaration :

$scope.updateUploadView = 
{
  ready:{
    inview:false,
    text: "starting"
  },
  uploading:{
    inview:false,
    text: "uploading"
  },
  done:{
    inview:false,
    text: "done !"
  }
};

$watch :

angular.forEach($scope.updateUploadView, function(element, key) {
  $scope.$watch(function () {
    return element;
  }, function() {
   // do stuff
  });
},true);
});

The problem here is that i want to ignore $watch to trigger on the undefined property because it cause the view to change 3 times on the start of the application. Is there any possibility to wait the variable declaration ?

http://jsfiddle.net/A8Vgk/2200/

throw that bunch of code into angular.element(document).ready(function(){ ... }); — Ji_in_coding
– Ji_in_coding, Commented Feb 4, 2016 at 22:57
too little information is know about your controller/parent controller/template(s) structure. It's really hard to guess what can possibly affect this. But you have said it has triggered 3 times. that should tell you something! 3 controllers? 3 views? 3 objects? think along those lines. I don't know what else to suggest, find the point where everything is ready before applying watcher — Ji_in_coding
– Ji_in_coding, Commented Feb 4, 2016 at 23:33
you probably simplified the fiddle example, it seems to be working perfectly fine — Ji_in_coding
– Ji_in_coding, Commented Feb 4, 2016 at 23:38

HankScorpio · Accepted Answer · 2016-02-05 00:12:01Z

1

Just check for undefined in your watch function.

$scope.$watch(function () {
  return element;
}, function(newValue, oldValue) {
  if(!angular.isDefined(newValue) && angular.isDefined(oldValue)) {
    // do stuff
  }
});

edited Feb 5, 2016 at 0:12

answered Feb 4, 2016 at 23:00

HankScorpio

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6 Comments

Francis Delgado Over a year ago

Well i was sure it would work but strangly it enter in the condition

HankScorpio Over a year ago

Then they must be defined. Check the newValue and oldValue, what are they?

Francis Delgado Over a year ago

I don't use them ( maybe i'm using totally the wrong method i'm pretty new to angular ) i put a link to a jsfiddle if you want to try it'll be easier for you.

HankScorpio Over a year ago

It appears to be working correctly, and since your data is present before you created the $watch, you don't even need to check for undefined as I suggested. It's firing the $watch once for each of the 3 watches you created. If this isn't what you're looking for, try using angular.equals() (see updated answer)

HankScorpio Over a year ago

actually, that doesn't work as I expected it to. Check out this post here for suggestions on how to skip the initial $watch stackoverflow.com/questions/16947771/…

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