javascript - Objects empty after code refactoring -

i don't understand why following code produces different outputs:

first algorithm:

var data = {     l1: 1,     l2: 2,     l3: 3 }; var datas = []; (var = 0; < 3; i++) {     datas[i] = {}     (key in data) {         datas[i][key] = data[key]     } }; delete datas[0].l1 delete datas[1].l2 delete datas[2].l3 console.log(data) console.log("%j", datas) 

output:

{ l1: 1, l2: 2, l3: 3 } [{"l2":2,"l3":3},{"l1":1,"l3":3},{"l1":1,"l2":2}] 

second algorithm:

var data = {     l1: 1,     l2: 2,     l3: 3 }; var datas = []; (var = 0; < 3; i++) {     datas[i] = {}     datas[i] = data ;  }; delete datas[0].l1 delete datas[1].l2 delete datas[2].l3 console.log(data) console.log("%j", datas) 

output:

{} [{},{},{}] 

following line second block/algo:

datas[i]=data  

you defining reference same object data (and not new objects). so, after delete properties data object, references reflect change.