angular.directive.ng:eval.html

<h1>angular.directive.ng:eval</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>The <code>ng:eval</code> allows you to execute a binding which has side effects 
without displaying the result to the user.</p>
<h2>Usage</h2>
<h3>In HTML Template Binding</h3>
<tt>
  <pre>
&lt;ANY ng:eval="expression"&gt;
  ...
&lt;/ANY&gt;
  </pre>
</tt>
<h3>Parameters</h3>
<ul>
    <li><tt>expression</tt> –
      <tt>&#123;expression&#125;</tt>
      <tt></tt>
      – to eval.</li>
  </ul>
<h2>Example</h2>
<p>Notice that <code>{{</code> <code>obj.multiplied = obj.a * obj.b</code> <code>}}</code> has a side effect of assigning 
a value to <code>obj.multiplied</code> and displaying the result to the user. Sometimes, 
however, it is desirable to execute a side effect without showing the value to 
the user. In such a case <code>ng:eval</code> allows you to execute code without updating 
the display.</p>
<doc:example>
  <doc:source>
&lt;input name="obj.a" value="6" &gt; 
  * &lt;input name="obj.b" value="2"&gt; 
  = {{obj.multiplied = obj.a * obj.b}} &lt;br&gt;
&lt;span ng:eval="obj.divide = obj.a / obj.b"&gt;&lt;/span&gt;
&lt;span ng:eval="obj.updateCount = 1 + (obj.updateCount||0)"&gt;&lt;/span&gt;
&lt;tt&gt;obj.divide = {{obj.divide}}&lt;/tt&gt;&lt;br/&gt;
&lt;tt&gt;obj.updateCount = {{obj.updateCount}}&lt;/tt&gt;
  </doc:source>
  <doc:scenario>   it('should check eval', function(){
     expect(binding('obj.divide')).toBe('3');
     expect(binding('obj.updateCount')).toBe('2');
     input('obj.a').enter('12');
     expect(binding('obj.divide')).toBe('6');
     expect(binding('obj.updateCount')).toBe('3');
   });</doc:scenario>
</doc:example>