Stack

栈，后进先出

class Stack {
    constructor() {
        this.list = []
    }

    pop() {
        const t = this.top()
        this.list.pop()
        return t
    }

    push(...item) {
        this.list.push(...item)
    }

    top() {
        return this.isEmpty() ? undefined : this.list[this.size() - 1]
    }

    size() {
        return this.list.length
    }

    isEmpty() {
        return this.list.length === 0
    }
}

Queue

队列，先进先出

class Queue {
    constructor() {
        this.list = []
    }

    dequeue() {
        const t = this.head()
        this.list.shift()
        return t
    }

    enqueue(...item) {
        this.list.push(...item)
    }

    head() {
        return this.isEmpty() ? undefined : this.list[0]
    }

    size() {
        return this.list.length
    }

    isEmpty() {
        return this.list.length === 0
    }
}

String拼接

考虑下面的方法

str = '';
for (/* each piece */) {
  str += piece; // bad for performance!
}
return str;

此方法将导致过多的中间字符串和连接操作，并且整体执行效果不佳

解决上面问题的方法是使用join

var tmp = [];
for (/* each piece */) {
  tmp.push(piece);
}
str = tmp.join(''); // Specified an empty separator, thanks Jonathan
return str;

此方法不会受到额外字符串对象的影响，并且通常执行得更快。