JSFiddle - React, Tailwind, and code Playground

JavaScript

var obj = {id: 'test_id', klass: 'test_class'};
alert(obj.id + ' ' + obj.class);

var obj = {id: 'test_id', klass: 'test_class'};
alert(obj['id'] + ' ' + obj['klass']);

var obj = {id: 'test_id', klass: 'test_class'};
for(key in obj) {
    alert(key);   
}