Copy array element modify and add again

Question

Original array is newData. I wanted add one more array element to newData and added array Element should have Rank 1.

Issue is Rank is getting updated to 1 for both the records. Rank should be 1 for second record and 1st record should be null

Please tell me what i'm doing wrong here.

let newData = [{
    "key1": {
        "cc":'IND'   
    },          
    "key2": {
        "rank": null
    }
}];

let setData = newData.concat(newData.slice());

setData.forEach(data => { 
    data.key2.rank =+ 1;
});

Possible duplicate of [How do I correctly clone a JavaScript object?](https://stackoverflow.com/questions/728360/how-do-i-correctly-clone-a-javascript-object) — ASDFGerte, May 23 '18 at 09:51

Nikhil Aggarwal · Accepted Answer · 2018-05-23T10:09:09.080

You can try following

let newData = [{"key1": {"cc":'IND' }, "key2": {"rank": null}}];

    // Concatenate arrays use spread operator and can use map rather than slice
    let setData = [...newData, ...newData.map(data => { 
        /* Objects are passed by reference, you need to break the reference
         * to create the clone of the object. */
        data = JSON.parse(JSON.stringify(data));
        data.key2.rank =+ 1; 
        return data;
    })];

console.log(setData);

score 0 · Answer 2 · answered May 23 '18 at 10:00

0

setData.forEach(data => { 
  data.key2.rank += 1;
});

Try to flip your operator from =+ to += instead

answered May 23 '18 at 10:00

Isaac

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if i use += 1, rank is changing to 2 for both the records – Arun K May 23 '18 at 10:06
@ArunK: If you don't mind can you construct the result that you're expecting and include in your question? – Isaac May 23 '18 at 11:17

Copy array element modify and add again

2 Answers2