【数据结构】JavaScript Queue 实现

完整可运行代码

class Queue {
  constructor() {
    this.count = 0
    // 队头
    this.head = 0
    this.items = {}
  }

  enqueue(element) {
    this.items[this.count] = element
    this.count++;
  }

  dequeue() {
    if (this.isEmpty()) {
      return undefined;
    }
    const result = this.items[this.head]
    delete this.items[this.head]
    this.head++
    return result
  }

  peek() {
    if (this.isEmpty()) {
      return undefined
    }
    return this.items[this.head]
  }

  isEmpty() {
    return this.size() === 0
  }

  clear() {
    this.items = {}
    this.count = 0
    this.head = 0
  }

  size() {
    return this.count - this.head
  }

  toString() {
    if (this.isEmpty()) {
      return ''
    }
    let objString = `${this.items[this.head]}`
    for (let i = this.head + 1; i < this.count; i++) {
      objString = `${objString},${this.items[i]}`
    }
    return objString
  }
}
// 
const queue = new Queue()

queue.enqueue('a')
queue.enqueue('b')
queue.enqueue('c')
queue.enqueue('d')
console.log(queue.toString()) //--> a,b,c,d

queue.dequeue()
queue.dequeue()
console.log(queue.toString()) //--> c,d

console.log(queue.peek()) //--> c

console.log(queue.isEmpty()) //--> false

console.log(queue.size()) //--> 2