var ar = ['one', 'two', 'three'];
var ar2 = ar; // assign ar to ar2
ar2[1] = 2; // modify element in ar2
// change to ar2 also changes ar
console.log( ar ); // ["one", 2, "three"]
console.log( ar2 ); // ["one", 2, "three"]
alert( ar === ar2 ); // true (ar and ar2 refer to the same object)