&gt;Disabled&lt;/button&gt;
&lt;/div&gt;
</code></pre>
<p>The HTML specification does not require browsers to preserve the values of boolean attributes
such as disabled. (Their presence means true and their absence means false.)
If we put an Angular interpolation expression into such an attribute then the
binding information would be lost when the browser removes the attribute.
The <code>ngDisabled</code> directive solves this problem for the <code>disabled</code> attribute.
This complementary directive is 