javascript deep copy members from array of objects

Question

I have a array of objects, looks like

[
  {Time: , //time stamp 
   psi:  //pressure value at the time
  }, 
  ... //other objects in the array the same
]

The array is named "data"

if I slice part of the array, and pass them to find local max and min values, would the code below deep copy and return the local extremes? How to verify?

var extreme = findLocalExtreme(data.slice(0, 10));  //slice(0, 10) for example, shallow copy

function findLocalExtreme(slicedArr){
  //error control skipped, the array could be empty or only 1 member
  let tempMax = slicedArr[0]; //would the "=" deep copy the object or just shallow copy? 
  let tempMin = slicedArr[0];
  let slicedArrLength = slicedArr.length;
  for (let i = 1; i < slicedArrLength; i++){
    if (slicedArr[i].psi > tempMax.psi){
      tempMax = slicedArr[I]; //deep copy or shallow copy?
    }
    if (slicedArr[i].psi < tempMin.psi){
      tempMin = slicedArr[i];
    }
  }
  return {
    Max: tempMax, 
    Min: tempMin //is the value assignment in returned class deep copy, or still shallow copy?
  }
}

Any advise welcome.

Alok Takshak · Accepted Answer · 2020-08-20 17:27:12Z

4

let tempMax = slicedArr[0] will just do the shallow copy instead you can do let tempMax = {...slicedArr[0]} since your object is only at level one this will do a deepcopy, if it is nested you can use loadash's cloneDeep to do a deepcopy.

Anywhere you are assiging a object to a variable it is a shallow copy

edited Aug 20, 2020 at 17:27

answered Aug 20, 2020 at 5:06

Alok Takshak

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su_sundariya · Accepted Answer · 2020-08-20 05:26:07Z

2

You can use loadsh cloneDeep method to copy objects or array.

import _ from 'loadsh';
let arr = [
            {name: 'temp'}
            {name: 'temp1}
       ]

let copyArr = _.cloneDeep(arr);

answered Aug 20, 2020 at 5:26

su_sundariya

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KcH · Accepted Answer · 2020-08-20 06:18:26Z

0

Deep Copy of a nested array of objects using JSON.parse(JSON.stringify(your_array_here))

reference link Deep Copy & Shallow Copy

//Deep Clone
let a = [{ x:{z:1} , y: 2}];
let b = JSON.parse(JSON.stringify(a));
b[0].x.z=0
console.log(a);
console.log(b);

answered Aug 20, 2020 at 6:18

KcH

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