Change form url query parameter with jquery on input change state
<p>Trying to create an "add to cart" button with quantity of items to add, i've added an <code>&lt;input id="product_quantity" value="1" onChange="updateQuantity()" /&gt;</code> to a main <code>form</code> so whenever i change a value inside that <code>input</code> it should update a form's action url withing a query parameter to corresponding value from <code>input</code> field.</p>

<p>Here is the overview in HTML:</p>

<pre><code>&lt;form action="index.php?option=com_virtuemart&amp;view=cart&amp;task=add&amp;virtuemart_product_id[]=1&amp;virtuemart_category_id[]=1&amp;quantity[]=1&amp;format=json"&gt;
    &lt;input type="product_quantity" value="1" onChange="updateQuantity();"/&gt;
    &lt;input type="submit" /&gt;
&lt;/form&gt;
</code></pre>

<p>So how to change a form's action url parameter string <code>&amp;quantity[]=XXX</code> to a specific value which is typed in <code>input</code>'s field ?</p>

<p>Thanks</p>
