Question 190887 in Javascript Question posted in
A very good W3school tutorial can be found here.

Optimizing Deep Clone in Javascript

I recently wrote this function for deep cloning an object in javascript, but with the given time complexity it would be extremely slow, any tips on making it more effecient?

function deepClone(obj){
  let clone = {};
  for (let k in obj){
    let v = obj[k];
    if (!array.isArray(v)&&("object"!==typeof v)){
      clone[k]=v;
      continue;
    } else {
      if (typeof v==="object"){
        let RCRSD = deepClone(v);
        clone[k]=RCRSD;
      } else {
        if (array.isArray(v)){
          let arr=[];
          for (let e of v){
            if (typeof e==="object"){
              arr.push(deepClone(e));
            } else {
              arr.push(e)
            };
            clone[k]=arr;
          };
        };
      };
    };
  };
};

This method also does not account for other data structures which is another problem

Tags:

2

Answers


  1. 0

    You can use recursion and check the value of the key

    function deepClone(obj) {
  if (obj === null) {
    return null;
  }
  // create a copy of the object
  let clone = Object.assign({}, obj);
  Object.keys(clone).forEach(
    key =>
    // if the value is another object then do recursion
    (clone[key] =
      typeof obj[key] === 'object' ? deepClone(obj[key]) : obj[key])
  );
  // if the value is an array then just make a new copy of the array
  if (Array.isArray(obj)) {
    clone.length = obj.length;
    return Array.from(clone);
  }
  return clone;
};


const a = {
  foo: 'bar',
  obj: {
    a: 1,
    b: 2
  }
};
const b = deepClone(a);
console.log(a !== b);
console.log(a.obj !== b.obj)
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  2. 0

    This isn’t necessarily more efficient (your code seems to be about there sans the weird conditionals), but it does address some bugs in your code (incorrectly handling arrays), and just a bit cleaner.

    function deepClone(obj) {
  if(obj === null) return null
  
  const target = {}
  for(const key in obj) {
    if(typeof obj[key] === "object") {
      if(Array.isArray(obj[key])) {
        target[key] = []
        for(let i = 0; i < obj[key].length; i++) {
          const curr = obj[key][i]
          target[key][i] = typeof curr === "object" ? deepClone(curr) : curr
        }
      } else target[key] = deepClone(obj[key])
    } else
      target[key] = obj[key]
  }
  return Array.isArray(obj) ? Object.values(target) : target
}

console.log(deepClone({
  hello: "world",
  one: {
    plus: {
      one: 1,
      equals: 2
    }
  },
  fiveWithInflation: 6,
  arr: [1, 2, { hello: [3] }, 4]
}))

console.log(deepClone([1, 2, 3]))
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