使用javaScript来实现一个单链表

1.创建链表节点

class Node{
    constructor(element,next){
        this.element = element;
        this.next = next;
    }
}

2.创建一个比较函数

function defaultEquals(a , b){
    return a == b;
}

3.创建一个单链表的类

class LinkedList {
        constructor(equalsFn = defaultEquals){
            this.head = undefined;
            this.count = 0;
            this.equalsFn = equalsFn;
        }
}

4.获取链表的长度

 size(){
            return this.count;
        }

5.判断链表是否为空

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

6.添加元素

        push(element){
            let node = new Node(element);
            if(this.head == undefined){//如果链表只有一个节点
                this.head = node;
            }else{
                let current = this.head;
                while(current.next!=null){//一直遍历到链表尾部
                    current = current.next;
                }
                current.next = node;
            }
            this.count++;
        }

7.获取指定位置的值

        getElementAt(index){
            if(index>=0 && index< this.count){
                let current = this.head;
                for(let i = 0; i < index && current != null; i++){
                    current = current.next;
                }
                return current;
            }
            return 'index out of range';
        }

8.查询值的位置

        indexOf(element){
            let current = this.head;
            for(let i = 0; i < this.count; i++){
                if(current.element === element){
                    return i;
                }
                current = current.next;
            }
            return -1;
        }

9.指定位置插入元素

        insert(element,position){
            if(position >=0 && position <= this.count){
                let node = new Node(element);
                if(position == 0){
                    if(this.head === undefined){
                        this.head = node;
                    }else{
                        node.next = this.head;
                        this.head = node;
                    }
                }else if(position == this.count){
                    let current = this.getElementAt(position - 1);
                    current.next = node;
                }else{
                    let previous = this.getElementAt(position - 1);
                    let current = previous.next;
                    node.next = current;
                    previous.next = node;                    
                }
                this.count++;
            }
            return "position out of range";
        }

10.删除元素

        remove(element){
            if(this.isEmpty())return "linkedlist is null";
            let index = this.indexOf(element);
            this.removeAt(index);
        }

11.删除指定位置的元素

        removeAt(index){
            if(this.isEmpty())return "linkedlist is null";
            if(index >= 0 && index < this.count){
                if(index == 0){//这里总是容易被忽略，如果index为0的话，就直接更改this.head
                    this.head = this.head.next;
                }else{
                    let previous = this.getElementAt(index -1);
                    let current = previous.next;
                    previous.next = current.next;
                   
                }
                this.count--;
            }
            return 'index out of range';
        }

12.打印链表的所有的值

        toString(){
            if(this.isEmpty())return 'linkedlist is null'
            let current = this.head.next;
            let objString = this.head.element;
            for(let i = 1; i < this.count; i++){
                objString = `${objString},${current.element}`;
                current = current.next;
            }
            return objString;
        }

13.完整代码

 class LinkedList {
        constructor(equalsFn = defaultEquals){
            this.head = undefined;
            this.count = 0;
            this.equalsFn = equalsFn;
        }
        size(){
            return this.count;
        }
        isEmpty(){
            return this.size() == 0;
        }
        push(element){
            let node = new Node(element);
            if(this.head == undefined){
                this.head = node;
            }else{
                let current = this.head;
                while(current.next!=null){
                    current = current.next;
                }
                current.next = node;
            }
            this.count++;
        }
        getElementAt(index){
            if(index>=0 && index< this.count){
                let current = this.head;
                for(let i = 0; i < index && current != null; i++){
                    current = current.next;
                }
                return current;
            }
            return 'index out of range';
        }
        indexOf(element){
            let current = this.head;
            for(let i = 0; i < this.count; i++){
                if(current.element === element){
                    return i;
                }
                current = current.next;
            }
            return -1;
        }
        insert(element,position){
            if(position >=0 && position <= this.count){
                let node = new Node(element);
                if(position == 0){
                    if(this.head === undefined){
                        this.head = node;
                    }else{
                        node.next = this.head;
                        this.head = node;
                    }
                }else if(position == this.count){
                    let current = this.getElementAt(position - 1);
                    current.next = node;
                }else{
                    let previous = this.getElementAt(position - 1);
                    let current = previous.next;
                    node.next = current;
                    previous.next = node;                    
                }
                this.count++;
            }
            return "position out of range";
        }
        remove(element){
            if(this.isEmpty())return "linkedlist is null";
            let index = this.indexOf(element);
            this.removeAt(index);
        }
        removeAt(index){
            if(this.isEmpty())return "linkedlist is null";
            if(index >= 0 && index < this.count){
                if(index == 0){//这里总是容易被忽略，如果index为0的话，就直接更改this.head
                    this.head = this.head.next;
                }else{
                    let previous = this.getElementAt(index -1);
                    let current = previous.next;
                    previous.next = current.next;
                   
                }
                this.count--;
            }
            return 'index out of range';
        }
        toString(){
            let current = this.head.next;
            let objString = this.head.element;
            for(let i = 1; i < this.count; i++){
                objString = `${objString},${current.element}`;
                current = current.next;
            }
            return objString;
        }
    }

14.结果