Find inputs with a [data-value-prop] attribute and set their value to the 'content' attribute of an children of $source whose [itemprop] matches the input's [data-value-prop].
<div id="item" itemscope>
<data itemprop="foo" content="1234">One, and a two-three-four!</data>
<meta itemprop="bar" content="raise the bar"/>
</div>
<form id="inputs">
<input name="item[foo]" type="text" data-value-prop="foo"/>
<input name="item[bar]" type="hidden" data-value-prop="bar"/>
</form>
$( '#inputs' ).populateDataProps( $( '#item' ) );
Afterwards, the form will have the following data:
{ "item": { "foo": 1234, "bar": "raise the bar" } }