iterators & generators in ecmascript 6.0
TRANSCRIPT
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
foreach (object obj in list) {DoSomething(obj);
}
Enumerator e = list.GetEnumerator();while (e.MoveNext()) {
object obj = e.Current;DoSomething(obj);
}
public interface IEnumerable{IEnumerator GetEnumerator();
}
public interface IEnumerator{object Current {get;}bool MoveNext();void Reset();
}
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
class Range{constructor(low, high){ this.low = low; this.high = high; }
[Symbol.iterator](){return new RangeIterator(this);
}}
class RangeIterator{constructor(range){ this.range = Range; this.current = this.range.low; }
next(){if( this.current > this.range.high ){
return { value : undefined, done : true };} else {
return { value : this.current++, done : false };}
}}
for( let i of new Range(1, 3) ) { console.log(i); }
// Like IEnumerable in C#
// Like IEnumerator in C#
// Like foreach in C#
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
var colors = new Set(['rojo', 'amarillo', 'azul']);
for (let word of colors){
alert(word); // "rojo", "amarillo", "azul" (the data)
}
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
let arr = [ "blue", "green" ];
arr.notAnIndex = 123;
Array.prototype.protoProp = 456;
for (let k in arr) {
console.log(k);
}
Print:
> 0
> 1
> notAnIndex
> protoProp
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
public class Test {public IEnumerator GetEnumerator() {
yield return "Hello"; yield return "World";
}}
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
public class Test {public IEnumerator GetEnumerator() {
return new __Enumerator(this);}
} private class __Enumerator : IEnumerator{object current;int state;
public bool MoveNext() {switch (state) {
case 0:current = "Hello";state = 1;return true;
case 1:current = "World";state = 2;return true;
default:return false;
}}public object Current { get { return current; } }
}
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
function *simpleGenerator(){
yield "Hello";
yield "World";
for (var i = 0; i < 2; i++)
yield i;
}
var g = simpleGenerator();
print(g.next()); // "Hello"
print(g.next()); // "World"
print(g.next()); // 0
print(g.next()); // 1
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
class Range{constructor(low, high){
this.low = low;this.high = high;
}*[Symbol.iterator](){
for (let i = this.low; i <= this.high; i++) {yield i;
}}
}
for (var i in new Range(3, 5) ) {print(i); // 3, 4, 5 in sequence
}
// Like IEnumerable in C#
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
function* g1() { yield 2; yield 3; }
function* g2() {yield 1;yield* g1();yield 4;
}
var iterator = g2();
console.log( iterator.next().value ); // 1console.log( iterator.next().value ); // 2console.log( iterator.next().value ); // 3console.log( iterator.next().value ); // 4
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
function* longRunningTask() {
let result1 = yield* step1();
yield;
let result2 = yield* step2();
yield;
yield* step3(result1, result2);
}
function* step1() { ... return result1; }function* step2() { ... return result2; }function* step3(p1, p2) { ... }
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
function* fibonacci() {let [prev, curr] = [0, 1];for (;;) {
[prev, curr] = [curr, prev + curr];yield curr;
}}
for (n of fibonacci()) {// truncate the sequence at 1000if (n > 1000)
break;print(n);
}
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
link
let items = [1, 2, 3, 4, 5, 6]
.asEnumerable()
.where(x => x % 2)
.select(x => x + 1);
for (let item in items) {
console.log(item);
}
//output will be 2, 4, 6
© 2015 Eyal Vardi. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
http://www.2ality.com/
Understanding ECMAScript 6
http://ecmascript6.org/
A Few New Things Coming To JavaScript
HARMONY OF DREAMS COME TRUE
Harmony specification_drafts
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