$watch is triggered directly after init, why?

Question

Why does $watch trigger directly after page load and how can I prevent this?

http://jsfiddle.net/dcSRu/2/

function MyCtrl($scope) {     // Init scope vars     $scope.data_copy = {};      // If data_copy changes...     $scope.$watch("data_copy", function(newValue, oldValue) {          alert("$watch triggered!");      }, true); } 

Answer 1

On first run both values (newValue and oldValue) are equal, so you may easily escape it by checking for equality:

$scope.$watch("data_copy", function(newValue, oldValue) {   if(newValue === oldValue){     return;   }   alert("$watch triggered!"); }); 

PLUNKER

Answer 2

Wrap $watch function into angular ready function.

angular.element(document).ready(function()  {    $scope.$watch("data_copy", function(newValue, oldValue) {     alert("$watch triggered!");   }, true); }) 

When angular loads page. It changes values and $watch is triggered.