This document discusses iterators in ES6. It explains that an object is considered iterable if it has a Symbol.iterator property implementation. Arrays, Maps, and Sets have built-in iterator implementations, while objects do not by default. The document provides examples of using for-of loops to iterate over arrays, sets, and customizes an object to be iterable by implementing Symbol.iterator.

1. Iterators | ES6
JAGADEESH PATTA ( PJ )

2. Agenda
 Introduction Iterators
 Iterator on Array
 Iterator on Set
 Iterator on Object
 Live Examples

3. Introduction
 An object is consider like an iterable when it has an implementation for
Symbol.iterator property.
 When an object contains Symbol.iterator implementation than the object
allows us to use in for…of on it.
 Array, Map, Set and String have their Symbol.iterator property already
implemented.

4. Iterator on Array
 An array has its own iterator function implementation.
Example
var arr_one = [ 1, 2, 3, 4, 5 ];
for ( let element of arr_one){
console.log ( arr_one [ element ] );
}

5. Iterator on Set
 An set has its own iterator function implementation.
Example
var set_one = ( [ 1, 2, 3, 4, 5 ] );
for ( let element of set_one){
console.log ( set_one [ element ] );
}

6. Iterator on Object
 An object doesn’t have its own iterator function implementation. If we want to
apply for…of on object we need to implement Symbol.iterator.
Example
var obj = {
“name” : “PJ”, “designation” : “SSE”
}

7. Iterator on Object (cont…)
Custom Iterator
obj [ Symbol.iterator ] = function( ) {
let keys = Object.keys (obj), count = 0, isDone = false;
let next = ( ) => {
if ( count >= keys.length ) { isDone = true }
return { done : isDone, value : obj [ keys [ count++ ] ] };
} return { next };
}

8. Iterator on Object (cont…)
Custom Iterator
for ( let property of obj ) {
console.log ( obj [ property ] );
}
// PJ, SSE

9. Any Q ?

10. Thank You