栈

有两种类似于数组的数据结构在添加和删除元素时更为可控，它们就是栈和队列。

栈数据结构

栈是一种遵从后进先出（LIFO）原则的有序集合

class stack {
    constructor() {
        this.items = [];
    }
    push(...elements) {
        return this.items.push(...elements)
    }
    pop() {
        return this.items.pop()
    }
    peek() {
        return this.items[this.items.length - 1];
    }
    isEmpty() {
        return Boolean(this.items.length)
    }
    clear() {
        this.items = [];
    }
    size() {
        return this.items.length;
    }
}

对于大量数据的使用使用一个对象来存储数据，查询效率更高

class stack {
    constructor() {
        this.count = 0;
        this.items = {};
    }
    push(...elements) {
        this.items[this.count] = elements;
        this.count++;
    }
    pop() {
        if (this.isEmpty()) {
            return undefined;
        }
        this.count--;
        const element = this.items[this.count]
        delete this.items[this.count]
        return element;
    }
    peek() {
        if (isEmpty()) {
            return undefined;
        }
        return this.items[this.count - 1];
    }
    isEmpty() {
        return this.count === 0;
    }
    clear() {
        this.items = {};
        this.count = 0;
    }
    size() {
        return this.count + 1;
    }
    toString() {
        if (this.isEmpty()) {
            return '';
        }
        let objString = `${this.items[0]}`; // {1}
        for (let i = 1; i < this.count; i++) { // {2}
            objString = `${objString},${this.items[i]}`; // {3}
        }
        return objString;
    }
}

私有属性/方法

新的提案通过#来声明私有属性

现阶段通过设置 Proxy 来禁止对类属性的访问

进制转换

十进制转二进制

function decimalToBinary(decNumber) {
  const remStack = new Stack();
  let number = decNumber;
  let rem;
  let binaryString = '';
  while (number > 0) { // {1}
    rem = Math.floor(number % 2); // {2}
    remStack.push(rem); // {3}
    number = Math.floor(number / 2); // {4}
  }
  while (!remStack.isEmpty()) { // {5}
    binaryString += remStack.pop().toString();
  }
  return binaryString;
}

和其他任意的进制转换

function convert(decNumber, base) {
  const remStack = [];
  const digs = '0123456789abcdefghijklmnopqrstuvwxyz'
  let number = decNumber;
  let rem;
  let binaryString = '';
  while (number > 0) {
    rem = Math.floor(number % base);
    remStack.push(rem);
    number = Math.floor(number / base);
  }
  while (!remStack.isEmpty()) { // {5}
    binaryString += digs[remStack.pop()];

    return binaryString;
  }
}

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