11. Iterators | ES6 | JavaScript | TypeScript
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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.
![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 ] );
}](https://image.slidesharecdn.com/11-170916115739/85/11-Iterators-ES6-JavaScript-TypeScript-4-320.jpg)
![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 ] );
}](https://image.slidesharecdn.com/11-170916115739/85/11-Iterators-ES6-JavaScript-TypeScript-5-320.jpg)
![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 };
}](https://image.slidesharecdn.com/11-170916115739/85/11-Iterators-ES6-JavaScript-TypeScript-7-320.jpg)
![Iterator on Object (cont…)
Custom Iterator
for ( let property of obj ) {
console.log ( obj [ property ] );
}
// PJ, SSE](https://image.slidesharecdn.com/11-170916115739/85/11-Iterators-ES6-JavaScript-TypeScript-8-320.jpg)
11. Iterators | ES6 | JavaScript | TypeScript
- 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