How to carry on the practice of JavaScript Design Model Iterator
Today, I will talk to you about the practice of how to carry out the JavaScript design model Iterator. Many people may not know much about it. In order to make you understand better, the editor has summarized the following contents for you. I hope you can get something according to this article.
Hands-on Iterator Pattern is a very important and simple Pattern: iterator!
We can provide an iterator with a unified entry. Client only needs to know what methods or Concrete Iterator are available, not how they are implemented at the bottom!
The main things of Iterator are two: hasNext and next. Let Client know if there is another one, and switch to the next one!
Define Interface
Interface IteratorInterface {index: number dataStorage: any hasNext (): boolean next (): any addItem (item: any): void}
Implementation interface
In the following example, I will use two common interfaces, Map and Array, to implement.
Class iterator1 implements IteratorInterface {index: number dataStorage: any [] constructor () {this.index = 0 this.dataStorage = []} hasNext (): boolean {return this.dataStorage.length > this.index} next (): any {return this.dataStorage [this.index + +]} addItem (item: any): void {this.dataStorage.push (item)}} / / mapclass iterator2 implements IteratorInterface {index: number dataStorage: Mapconstructor () { This.index = 0 this.dataStorage = new Map ()} hasNext (): boolean {return this.dataStorage.get (this.index)! = undefined} next (): any {return this.dataStorage.get (this.index + +)} addItem (item: any): void {this.dataStorage.set (this.dataStorage.size) Item)}}
Client
I did not implement a Client, so I am directly new a category out of direct use!
Const I = new iterator1 () i.addItem, i.addItem (456) i.addItem ('dolphin') while (i.hasNext ()) {console.log (i.next ())} console.log (`=`) const i2 = new iterator2 () i2.addItem (123) i2.addItem (456) i2.addItem (' dolphin') while (i2.hasNext ()) {console.log (i2.next ())}
You will find that the results of Iterator No.1 and No.2 are all the same! They all just need to let Client know that there is hasNext and next, and the underlying implementation does not need to let them know!
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