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October 20, 2022 18:03
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Testing implementation of HistoryList
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| class HistoryList { | |
| private readonly items: string[] = []; | |
| private index = -1; | |
| constructor(private readonly size = 100) {} | |
| push(val: string): void { | |
| this.items.push(val); | |
| while (this.items.length > this.size) { | |
| this.items.shift(); | |
| } | |
| this.index = -1; | |
| } | |
| previous(): string { | |
| if (this.index === -1) { | |
| this.index = this.items.length - 1; | |
| return this.items[this.index]; | |
| } | |
| if (this.hasPrevious) { | |
| return this.items[--this.index]; | |
| } | |
| return this.items[this.index]; | |
| } | |
| private get hasPrevious(): boolean { | |
| return this.index >= 1; | |
| } | |
| next(): string { | |
| if (this.index === this.items.length - 1) { | |
| this.index = -1; | |
| return ''; | |
| } | |
| if (this.hasNext) { | |
| return this.items[++this.index]; | |
| } | |
| return ''; | |
| } | |
| private get hasNext(): boolean { | |
| return this.index >= 0 && this.index !== this.items.length - 1; | |
| } | |
| } | |
| var historylist: HistoryList = new HistoryList(10); | |
| historylist.push('one'); | |
| historylist.push('two'); | |
| historylist.push(''); | |
| historylist.push('three'); | |
| console.log(historylist.next()); | |
| console.log(historylist.previous()); | |
| console.log(historylist.next()); | |
| console.log(historylist.previous()); | |
| console.log(historylist.previous()); | |
| console.log(historylist.previous()); | |
| console.log(historylist.previous()); | |
| console.log(historylist.previous()); | |
| console.log(historylist.next()); | |
| console.log(historylist.next()); | |
| console.log(historylist.next()); | |
| console.log(historylist.next()); | |
| console.log(historylist.next()); |
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Expected
oneas output when the firstnext()method is run. Howevertwois printed.