Assigning a temporary variable to a JSON

Question

I was trying to copy the contents of a particular JSON to another JSON and modify the temporary variable to my needs but the original JSON is also getting changed.

For example :

count = {
    passed : 2,
    failed : 5
} 
console.log(count)   // logs the JSON content
let temp = count;
console.log(temp)   // logs the JSON content

Say, now I'm modifying the temp, like :

temp.passed = 0;
console.log(temp);   //{passed : 0, failed : 5}

It is also changing the passed value of count too. Now if I log JSON of count,

console.log(count);    //{passed : 0, failed : 5}

where I want the passed to be 2, since I only modified the JSON object of passed in temp.

I want to keep the count to be same and modify only the temp. Can someone help me out ?

[That is not JSON, that is _an object_.](https://stackoverflow.com/questions/3975859/what-are-the-differences-between-json-and-javascript-object) — msanford, Feb 07 '18 at 18:42
you have to clone the object. you are just reassigning a reference. — Daniel A. White, Feb 07 '18 at 18:42
are you using any libraries: JQuery, Angular, underscoreJs?? — Kenry Sanchez, Feb 07 '18 at 18:43
In your example temp is pointing to your count object. You don't have two object. — Nesan Mano, Feb 07 '18 at 18:46

msanford · Answer 1 · 2018-02-07T19:08:51.390

1

First, that is not JSON, that is an "object literal". They are different things.

You need to clone the object, such as with a destructuring assignment:

count = {
  passed: 2,
  failed: 5
}

const temp = { ...count };

temp.passed = 0;

console.dir(temp);
console.dir(count);

Or with Object.assign() and an empty object, proposed by Kenry.

edited Feb 07 '18 at 19:08

answered Feb 07 '18 at 18:44

msanford

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score 1 · Answer 2 · answered Feb 07 '18 at 18:47

1

You must clone your object to add more properties and don't change the source.

Use Object.assign()

let temp = Object.assign({}, count);

In this way, you can add more properties without change the source.

answered Feb 07 '18 at 18:47

Kenry Sanchez

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Assigning a temporary variable to a JSON

2 Answers2