var objtext = '{ "employees" : [' +
'{ "firstName":"Bill" , "lastName":"Gates" },' +
'{ "firstName":"Steve" , "lastName":"Jobs" },' +
'{ "firstName":"Alan" , "lastName":"Turing" } ]}';
var obj = JSON.parse(objtext);
document.getElementById("demo").innerHTML=obj.employees[0].firstName;
<div id="demo"></div>