Zendesk Chat - identify customer and show widget

document_head.js

<script>
  <!-- Opens the chat widget automatically
	Example: https://SUBDOMAIN.zendesk.com/hc?start_chat=true&customer_name=John&customer_email=john@example.com
	-->
  jQuery.extend({
		getQueryParameters : function(str) {
			return (str || document.location.search).replace(/(^\?)/,'').split("&").map(function(n){return n = n.split("="),this[n[0]] = n[1],this}.bind({}))[0];
		}
	});
  
  var queryParams = $.getQueryParameters();

	if(queryParams["start_chat"]) {		
		zE(function() {
			zE.identify({
				name: queryParams["customer_name"],
				email: queryParams["customer_email"]
			});
			zE.activate();
		});
	}
</script>