Today I needed to write a function in jQuery to find and replace input value by name if it exists, otherwise append the input field to my html.

    $('tr').click(function() {
        var href = $(this).find("a").attr("href");
        if(href) {
			foundedit = $('input[name=permission_edit]').val();
			if(foundedit){
				$('input[name=permission_edit]').val(function(index, value) {
				   return value.replace(/\d+/,href);
				});
			} else {
				$("#permissions_form").append("<input type=\"hidden\" id=\"permission_edit\" name=\"permission_edit\" value=" + href + " />");
			}
        }
    });