Check if an object has a property

Question

How can I check if an object has a certain property in AngularJS?

If you don't know the name of property then you can simply check Object.keys(objName).length. I hope this helps. — Virendra Singh Rathore, Oct 27 '16 at 11:50

score 40 · Answer 1 · edited Feb 07 '18 at 11:39

40

You could use 'hasOwnProperty' to check if object have the specific property.

if($scope.test.hasOwnProperty('bye')){
  // do this   
}else{
  // do this then
}

Here's a demo in jsFiddle.

Hope this helpful.

edited Feb 07 '18 at 11:39

Kaleem Elahi

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answered Dec 09 '13 at 07:07

Chickenrice

5,727
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i pass object through directive (with '=') and in my directives controller I have this code snippet for initialization but I get TypeError: Cannot call method 'hasOwnProperty' of undefined. do you know why? – Daniel R Dec 09 '13 at 07:48
@user2985439: It sounds like your object does not have a property `test`. – Felix Kling Dec 09 '13 at 07:52
@user2985439 As Felix Kling mentioned, the object your directive referenced doesn't have 'test' property. Could you update your question for more details? – Chickenrice Dec 09 '13 at 08:01
scope: {test:'='},controller($scope) {if($scope.test.hasOwnProperty('bye')) {// do stuff}} this returns the type error. I know test is defined because I pass it right through in the view... – Daniel R Dec 09 '13 at 08:02
Does the blash directive in the controller scope ? My blash directive just work as expected. [demo](http://jsfiddle.net/J83Ch/3/) – Chickenrice Dec 09 '13 at 08:32
Suppose if i have an object whose keys are leveled let's assume obj.key1.key2.key3 then how can i check key3 exist in obj in one call. – Virendra Singh Rathore Dec 07 '16 at 13:03

score 2 · Answer 2 · answered Dec 09 '13 at 07:10

2

if('bye' in $scope.test) {}
else {}

answered Dec 09 '13 at 07:10

codebreach

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score 1 · Answer 3 · answered Dec 09 '13 at 21:39

The problem is that you probably will have value not just when linking your directive - it could be loaded by $http for example.

My advice would be:

controller: function($scope) {
  $scope.$watch('test.hello', function(nv){ 
     if (!nv) return; 
     // nv has the value of test.hello. You can do whatever you want and this code
     // would be called each time value of 'hello' change
  });
}

or if you know that the value is assigned only one:

controller: function($scope) {
  var removeWatcher = $scope.$watch('test.hello', function(nv){ 
     if (!nv) return; 
     // nv has the value of test.hello. You can do whatever you want
     removeWatcher();
  });
}

This code will remove watcher the value of 'test.hello' was assigned (from any controller, ajax, etc etc)

Check if an object has a property

3 Answers3