Implementation for Object.entries

objectEntries.js

// Alt 1
Object.prototype.entries = function() {
  let keys = Reflect.ownKeys(this).values()
  
  return {
    [Symbol.iterator]() {
      return this
    },
    next: () => {
       let { done, value: key } = keys.next()
       if (!done) {
         return { value: [key, this[key]] }
       }
       return { done }
    }
  }
}

// Alt 2
Object.prototype.entries = function() {
  let key
  let keys = Reflect.ownKeys(this)
  
  return {
    [Symbol.iterator]() {
      return this
    },
    next: () => {
       if ((key = keys.shift()) !== undefined) {
         return { value: [key, this[key]] }
       }
       return { done: true }
    }
  }
}

// Alt 3 -- So simple
Object.prototype.entries() {
  return Reflect.ownKeys(this).map(key => [key, this[key]])
}


// Example Usage
for (let [key, value] of { a: 1, b: 2, c: 3 }.entries()) {
  console.log(key, ':', value)
}
// a : 1
// b : 2
// c : 3