this will treat [1,2,3] and [3,2,1] as equal (deep object)
since I needed to visualize the difference between:
[
  {
    "a":1,
    "b":1
  },
  {
    "a":1,
    "b":1
  }
]
and
[
  {
    "a":1,
    "b":1
  },
  {
    "a":"OH NO",
    "b":"an insertion"
  },
  {
    "a":1,
    "b":1
  }
]
so I wanted to see them collide, here's what's left:
[]
and
[
  {
    "a":"OH NO",
    "b":"an insertion"
  }
]
imo this is the best way to represent it.
{add:{...},upd:{...},del:{...}} is hard to read
I provide 2 functions : ObjectCollide(obj1,obj2) and ArrayCollide(arr1,arr2)
console.log(ArrayCollide([1,2,3],[3,2,1]))
// false
//everything collided -> false
console.log(ArrayCollide([1],[2,1]))
// [ [], [ 2 ] ]
//1 and 1 collided, even if they are on different indices
//array of objects
const arr1 = 
[
  {
    "a":1,
    "b":1
  },
  {
    "a":1,
    "b":1
  }
]
const arr2 = 
[
  {
    "a":1,
    "b":1
  },
  {
    "a":"OH NO",
    "b":"an insertion"
  },
  {
    "a":1,
    "b":1
  }
]
const newArrays = ArrayCollide(arr1, arr2)
console.log(newArrays[0])
console.log(newArrays[1])
console.log('\n')
// []
// [ { a: 'OH NO', b: 'an insertion' } ]
// everything collided until this is left
//ObjectCollide
const obj1 = { a: '111', c: { q: 'no', a: '333' } }
const obj2 = { a: '111', p: 'ok', c: { a: '333' } }
ObjectCollide(obj1, obj2) //in place
console.log(obj1)
console.log(obj2)
console.log('\n')
// { c: { q: 'no' } }
// { p: 'ok', c: {} }
// obj["a"] collided and obj["c"]["a"] collided
//testing empty array
const a1 = { a: [] }
const a2 = { a: [], b: '2' }
ObjectCollide(a1, a2) //in place
console.log(a1)
console.log(a2)
console.log('\n')
// {}
// { b: '2' }
// obj["a"] collided
//DIFFERENT TYPES
const b1 = {a:true}
const b2 = {a:[1,2]}
ObjectCollide(b1,b2) //in place
console.log(b1)
console.log(b2)
// { a: true }
// { a: [ 1, 2 ] }
function ObjectCollide(obj1, obj2) {
  //in place, returns true if same
  // delete same
  const keys = Object.keys(obj1)
  const len = keys.length
  let howManyDeleted = 0
  for (let i = 0; i < len; i++) {
    const key = keys[i]
    const type1 = Array.isArray(obj1[key]) === true ? 'array' : typeof obj1[key]
    const type2 = Array.isArray(obj2[key]) === true ? 'array' : typeof obj2[key]
    if (type1!==type2) {
      continue
    }
    switch (type1) {
      case 'object':
        if (ObjectCollide(obj1[key], obj2[key])) {
          delete obj1[key]
          delete obj2[key]
          howManyDeleted++
        }
        continue
      case 'array':
        const newArrays = ArrayCollide(obj1[key], obj2[key])
        if (newArrays) {
          obj1[key] = newArrays[0]
          obj2[key] = newArrays[1]
        } else {
          delete obj1[key]
          delete obj2[key]
          howManyDeleted++
        }
        continue
      default:
        //string, number, I hope it covers everything else
        if (obj1[key] === obj2[key]) {
          delete obj1[key]
          delete obj2[key]
          howManyDeleted++
        }
    }
  }
  if (howManyDeleted === len && Object.keys(obj2).length === 0) {
    // return 'delete the stuff'
    // same. we've deleted everything!
    return true
  }
}
function ArrayCollide(arr1, arr2) {
  // returns [newArr1, newArr2] or false if same arrays (ignore order)
  const stringifyObj = {}
  const newArr1 = []
  const newArr2 = []
  for (let i = 0, len = arr1.length; i < len; i++) {
    const value = arr1[i]
    const stringified = JSON.stringify(value)
    stringifyObj[stringified]
    // arr = [count, ...]
    const arr = stringifyObj[stringified] || (stringifyObj[stringified] = [0])
    arr[0]++
    arr.push(value)
  }
  //in 2 but not in 1
  for (let i = 0, len = arr2.length; i < len; i++) {
    const value = arr2[i]
    const stringified = JSON.stringify(value)
    const arr = stringifyObj[stringified]
    if (arr === undefined) {
      newArr2.push(value)
    } else {
      if (arr[0] === 0) {
        newArr2.push(value)
      } else {
        arr[0]--
      }
    }
  }
  //in 1 but not in 2
  stringifyKeys = Object.keys(stringifyObj)
  for (let i = 0, len = stringifyKeys.length; i < len; i++) {
    const arr = stringifyObj[stringifyKeys[i]]
    for (let i = 1, len = arr[0] + 1; i < len; i++) {
      newArr1.push(arr[i])
    }
  }
  if (newArr1.length || newArr2.length) {
    return [newArr1, newArr2]
  } else {
    return false
  }
}
what I was trying to solve:
JSON file keeps reordering, I want to revert the JSON if it's equivalent: like {a:1,b:2} and {b:2,a:1}
but because I don't trust my code (I made a mistake once), I want to see the diff and check it myself, I can Ctrl+F into the original file using this diff.