jQuery/Javascript Invalid left-hand side in assignment
<p>I am using this relatively simple code:</p>

<pre><code>var height = help ? 'minus' : 'plus';
var prop = $('#properties');

if(height == 'minus'){
    prop.height(prop.height() -= 206);
} else {
    prop.height(prop.height() += 206);
}
</code></pre>

<p>It fails on both lines that do the adding/subtracting! Any ideas?</p>
