<p>I have a form I am submitting using jQuery's ajaxSubmit function from the Forms plugin. I'm trying to add a form name/value pair to the form data just before submission occurs. My plan is to modify the form data in the beforeSubmit event handler.</p>

<p>Given a function that looks like:</p>

<pre><code>function handleActionFormBeforeSubmit(formData, form, options) {
    // Add a name/value pair here somehow to formData
}
</code></pre>

<p>How do I add a simple pair to formData? It is an array in the form of:</p>

<pre><code>[ { name: 'username', value: 'jresig' }, { name: 'password', value: 'secret' } ]
</code></pre>

<p>Thanks,
Brian</p>

After an hour of experimentation, I figured out a solution. To append a value to the form data, the following code will work.
```
```
function handleActionFormBeforeSubmit(formData, form, options) {

    // Add a name/value pair indicating this is an asynchronous call.
    // This works with the ASP.NET MVC framework's Request.IsMvcAjaxRequest() method.
    formData[formData.length] = { "name": "__MVCASYNCPOST", "value": "true" };
}
```
```
You can also modify the data if you know the index of the value you want to change such as:
```
```
formData[0].value = 'new value';
```
```
I hope this helps someone else.