If that is your data then no problem. You missed the javascript array push method.
Please check the code
var array =[{"AutoKey":1,"MachineGroup":"Atyc","StartDate":"\/Date(1322002860000)\/","EndDate":"\/Date(1322027095000)\/","Duration":24235},{"AutoKey":2,"MachineGroup":"Fongs","StartDate":"\/Date(1322003160000)\/","EndDate":"\/Date(1322012194000)\/","Duration":9034},{"AutoKey":3,"MachineGroup":"Then","StartDate":"\/Date(1322005320000)\/","EndDate":"\/Date(1322019001000)\/","Duration":13681}];
console.log(array.length);
var newArray = [];
for(var i=0, j=array.length; i<j; i++){
newArray.push(array[i]);
}
console.log(newArray.length);