Fast way of getting difference between 2 objects

Question

Because my code will need to run this a lot, I need a very fast code to get the difference between 2 objects. Deleted properties should have a value of "deleted".

Example:

Object 1

{a: "hi", b: "hi", c: {o: "hi", p: "hi",}, d: ["hi", "bye"]}

Object 2

{a: "hi", b: "bye", c: {o: "bye",}, e: "new"}

Result

{b: "bye", c: {o: "bye", p: "deleted"}, d: "deleted", e: "new"}

how to process `d: ["hi", "bye"]` when for example only `'bye'` is deleted? — Alexander Nenashev, Aug 20 '23 at 12:06
What happens for `o1 = { a: [ { "foo": 1}]}` and `o2 = { a: [{"bar": 2}]}` — derpirscher, Aug 20 '23 at 13:07

Alexander Nenashev · Accepted Answer · 2023-08-21T13:45:01.917

2

You could use some recursive function to handle objects. It's not clear whether you need to handle arrays too

const old = {a: "hi", b: "hi", c: {o: "hi", p: "hi",}, d: ["hi", "bye"]}
const cur = {a: "hi", b: "bye", c: {o: "bye", f: "new"}, e: "new"};

const diff = (old, cur, result = {}) => {

  for(const k in cur){
    if(Object.is(old[k], cur[k])){
      continue;
    }
    if(cur[k].__proto__ === Object.prototype){
        diff(old[k], cur[k], result[k] = {});  
    }else{
      result[k] = cur[k];
    }
  }
  for(const k in old){
    if(!(k in cur)){
      result[k] = 'deleted';
    }
  }
  return result;

};



console.log(diff(old, cur));

edited Aug 21 '23 at 13:45

answered Aug 20 '23 at 12:05

Alexander Nenashev

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I forgot to mention that properties may be added too – hmmmm Aug 21 '23 at 13:27
@hmmmm add this to your code and i'll add it to the answer – Alexander Nenashev Aug 21 '23 at 13:31
ok i have edited my post – hmmmm Aug 21 '23 at 13:34
@hmmmm fixed... – Alexander Nenashev Aug 21 '23 at 13:45

Fast way of getting difference between 2 objects

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