Memo.js

var compare = function (obj1, obj2) {
    if (obj1 === obj2) {
      return true
    }
  
    var keyMap = {}
    var obj1Keys = Object.keys(obj1)
    var obj2Keys = Object.keys(obj2)
    
    
    for(let key of obj1Keys) {
      keyMap[key] = obj1[key]
    }
  
    for(let key of obj2Keys) {
      if (keyMap[key] && keyMap[key] === obj2[key]) {
        delete keyMap[key]
      } else {
        return false
      }
    }
    
    return Object.keys(keyMap).length === 0
}


function memo (fn) {
  var map = new Map()
  
  return function (arg) {  
    let returnVal = null 
    
    map.forEach((value, key) => {
      if (compare(key, arg)) {
        returnVal = value
      }
    })
  
    if (returnVal) {
      return returnVal
    } else {
      map.set(arg, fn(arg))
      return map.get(arg)
    }
  
  }
}

const memoFunc = memo(person)


function person (obj) {
  console.log('called')
  return obj.firstName + ' ' + obj.lastName
}


console.log(memoFunc({firstName: 'abhinav', lastName: 'sharma'}))
console.log(memoFunc({firstName: 'abhinav', lastName: 'sharma'}))
console.log(memoFunc({firstName: 'kanika'}))
console.log(memoFunc({firstName: 'kanika'}))
console.log(memoFunc({firstName: 'kanika1'}))