issue to modify an object value in javascript

Question

I have the following code.

var emp={"EmployeeLists":[{"ID":1,"NAME":"Anbu","Salary":80000},{"ID":2,"NAME":"Anand","Salary":90000}]};

// Inserting a new object into EmployeeLists
emp.EmployeeLists.splice(2,0,emp.EmployeeLists[1])
console.log(JSON.stringify(emp));

Output: {"EmployeeLists":[{"ID":1,"NAME":"Anbu","Salary":80000},{"ID":2,"NAME":"Anand","Salary":90000},{"ID":2,"NAME":"Anand","Salary":90000}]}

// Modifying inserted object NAME Anand into MANI
emp.EmployeeLists[2].NAME="MANI";
console.log(JSON.stringify(emp));

Output: {"EmployeeLists":[{"ID":1,"NAME":"Anbu","Salary":80000},{"ID":2,"NAME":"**MANI**","Salary":90000},{"ID":2,"NAME":"**MANI**","Salary":90000}]}

After added a new object. I tried to modify the name of that object Anand to MANI but it is modified name of object Two and Three.

Your question is unclear, can you explain exactly what you want to do ? — nanobash
– nanobash, Commented Mar 29, 2014 at 7:51

Community · Accepted Answer · 2017-05-23 12:28:49Z

1

Great question! What you are seeing is underlying sharing of objects, because Javascript secretly treats objects like pointers in C if you are not careful. Let's rewrite this to make a clone of the object instead. We will use this previous Stackoverflow answer (cloning objects in Javascript is annoying to do in full generality).

function clone(obj) {
    if (null == obj || "object" != typeof obj) return obj;
    var copy = obj.constructor();
    for (var attr in obj) {
        if (obj.hasOwnProperty(attr)) copy[attr] = obj[attr];
    }
    return copy;
}

emp.EmployeeLists.splice(2, 0, clone(emp.EmployeeLists[1]));
emp.EmployeeLists[2].NAME = "MANI";
// {"EmployeeLists":[{"ID":1,"NAME":"Anbu","Salary":80000},{"ID":2,"NAME":"Anand","Salary":90000},{"ID":2,"NAME":"MANI","Salary":90000}]}

edited May 23, 2017 at 12:28

CommunityBot

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answered Mar 29, 2014 at 8:08

Robert Krzyzanowski

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