$('ul li').each(function(index) {
	var spanContent = $(this).children('span').html(),
	spanContent = spanContent.toLowerCase().replace(/ /g, '-');
	$(this).children('input').attr('id', 'input-'+spanContent);
	$(this).children('span').wrapInner('<label for="input-'+spanContent+'"/>');
});

<ul>
<li><input type="checkbox" name="input-name-1" value="" /><span>Description 1</span></li>
<li><input type="checkbox" name="input-name-2" value="" /><span>Description 2</span></li>
<li><input type="checkbox" name="input-name-3" value="" /><span>Description 3</span></li>
</ul>

$('ul li').each(function(index) {
	var spanContent = $(this).children('span').html(),
	spanContent = spanContent.toLowerCase().replace(/ /g, '-');
	$(this).children('input').attr('id', 'input-'+spanContent);
	$(this).children('span').wrapInner('<label for="input-'+spanContent+'"/>');
});

Dynamically add <label> HTML tag to input description, matching the input by adding an ID value to the input.

Add \'label for\'  matching input dynamically

form, javascript, html, jquery

jQuery