JSFiddle - React, Tailwind, and code Playground

HTML

<span id="spResults"></span>

JavaScript

var x = [
	'{"id":"item1","val":"Items"}',
	'{"id":"item1","val":"Items"}',
	'{"id":"item2","val":"Items"}'
];    

var clickId = [];
$.each(x, function(index, value){
    var item = JSON.parse(value);
	if(clickId.indexOf(item.id) === -1){
		clickId.push(item.id);
	}
});

$('#spResults').html(clickId.join());