angular.scope.$watch.html

<h1>angular.scope.$watch</h1>
<fieldset class="workInProgress">
  <legend>Work In Progress</legend>
  This page is currently being revised. It might be incomplete or contain inaccuracies.
  
</fieldset>
<h2>Description</h2>
<p>Registers <code>listener</code> as a callback to be executed every time the <code>watchExp</code> changes. Be aware
that callback gets, by default, called upon registration, this can be prevented via the
<code>initRun</code> parameter.</p>

<h2>Example</h2><div ng:non-bindable><pre class="brush: js; html-script: true;">
         var scope = angular.scope();
         scope.name = 'misko';
         scope.counter = 0;

         expect(scope.counter).toEqual(0);
         scope.$watch('name', 'counter = counter + 1');
         expect(scope.counter).toEqual(1);

         scope.$eval();
         expect(scope.counter).toEqual(1);

         scope.name = 'adam';
         scope.$eval();
         expect(scope.counter).toEqual(2);
       </pre></div>
<h2>Usage</h2>
<tt ng:non-bindable>
angular.scope.$watch(watchExp, listener, exceptionHanlder, initRun);
</tt>
<h3>Parameters</h3>
<ul>
    <li><tt>watchExp</tt> –
      <tt>&#123;function()|string&#125;</tt>
      <tt></tt>
      – Expression that should be evaluated and checked for
   change during each eval cycle. Can be an angular string expression or a function.</li>
    <li><tt>listener</tt> –
      <tt>&#123;function()|string&#125;</tt>
      <tt></tt>
      – Function (or angular string expression) that gets called
   every time the value of the <code>watchExp</code> changes. The function will be called with two
   parameters, <code>newValue</code> and <code>oldValue</code>.</li>
    <li><tt>exceptionHanlder</tt> –
      <tt>&#123;(function()|DOMElement)=&#125;</tt>
      <tt>[angular.service.$exceptionHandler]</tt>
      – Handler
   that gets called when <code>watchExp</code> or <code>listener</code> throws an exception. If a DOMElement is
   specified as handler, the element gets decorated by angular with the information about the
   exception.</li>
    <li><tt>initRun</tt> –
      <tt>&#123;boolean=&#125;</tt>
      <tt>[true]</tt>
      – Flag that prevents the first execution of the listener upon
   registration.</li>
  </ul>