array-entries-keys.js

// ==========  arr.entries ===========
// "entries" return an iterator
var a = ['a', 'b', 'c'];
var iterator = a.entries();

for (let e of iterator) {
  console.log(e);
}
// [0, 'a']
// [1, 'b']
// [2, 'c']

//=================

var array1 = ['a', 'b', 'c'];
var iterator1 = array1.entries();

console.log(iterator1.next().value);
// expected output: Array [0, "a"]

console.log(iterator1.next().value);
// expected output: Array [1, "b"]
//==================================


//========== arr.keys =================
// The keys() method returns a new Array Iterator object
// that contains the keys for each index in the array.

var array1 = ['a', 'b', 'c'];
var iterator = array1.keys();

for (let key of iterator) {
  console.log(key); // expected output: 0 1 2
}