Add classes to selectbox options that should theoretically match possible referring URL slugs; get the referring URL and select the option that matches. Being used to choose a WooCommerce variation relevant to the grouped product that the user came from.

select-referrer-option.js

jQuery(document).ready(function() {

	var referrer =  document.referrer;
	var urlArray = referrer.split('/');
	var referrerSlug = urlArray.slice(-1)[0];

	jQuery("select#location > option").each(function() {
		var label = this.value; 
		label = label.replace(/\s+/g, '-').toLowerCase(); //lower case and replace spaces with hyphens
		label = label.replace("'", ""); //strip apostrophes
		jQuery(this).addClass(label); 
		if (jQuery(this).hasClass(referrerSlug)) {
			jQuery(this).prop('selected', true);
		}
	});

});