what is next() method?

Question

<script>
var fruits = ["Banana", "Orange", "Apple", "Mango"];
var x = fruits.keys();

document.getElementById("demo").innerHTML = x.next().value;
//output 0
</script>

Answer 1

Array.prototype.keys()

returns a new Array Iterator object that contains the keys for each index in the array.

And indexes are 0, 1, 2, 3

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/keys

Generator.prototype.next()

returns an object with two properties done and value.

without argument yields first object { value : 0, done : false}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Generator/next

so, fruits.keys().next().value is 0