//配列を作成
var array = { 0:"a" , 1:"b" , 2:"c" };

//配列をコピー
var newArray = JSON.parse(JSON.stringify(array));

//配列を変更
array[0] = "d";

//結果を表示
console.log(array);
console.log(newArray);

//console.logの結果
//array → {0: "d", 1: "b", 2: "c"}
//newArray → {0: "a", 1: "b", 2: "c"}