Javascript Recursion inside class method（此行为）

Question

问题在于 toString 函数内部，这并没有实现函数调用自己的范围：我需要一些东西来解决问题，'这'是javascript中最糟糕的，我已经在python中实现了确切的数据结构和函数，并且它有效...，我已经尝试过绑定和箭头函数，也许你可以帮我解决...代码的预期结果如下：1|__2   |__3      |__4         |__5class Node {    constructor(data){        this.data = data;        this.parent = null;        this.children = [];        Node.nodes.push(this);        this.index = Node.nodes.length;    }    addChild(node){        node.parent = this;        this.children.push(node);    }    getLevel(){        let level = 0;        while(this.parent){            level+=1;            this.parent = this.parent.parent;        }        //console.log('lvl',level);        return level;    }     toString (){        // console.log('lvl',this.getLevel());        let prefix = " ".repeat(this.getLevel()*3);        prefix += this.getLevel()===0 ? "" :"|__";        console.log(prefix + this.index);        if(this.children){            for(let i = 0; i < this.children.length; i++){                this.children[i].toString();            }        }    }    pathToRoot(){        return 0;    }}Node.nodes = [];const main = (()=>{let root = new Node('root');let kid1 = new Node('kid1');let kid2 = new Node('kid2');let kid3 = new Node('kid3');let kid4 = new Node('kid4');root.addChild(kid1);kid1.addChild(kid2);kid2.addChild(kid3);kid3.addChild(kid4);console.log('kid4 lvl :',kid4.getLevel())root.toString(root);})()

Answer 1

在循环中分配父项的父项。而是使用变量来循环父项。

class Node {

    constructor(data) {

        this.data = data;

        this.parent = null;

        this.children = [];

        if (!Node.nodes) Node.nodes = [];

        Node.nodes.push(this);

        this.index = Node.nodes.length;

    }

   

    addChild(node) {

        node.parent = this;

        this.children.push(node);

    }

    getLevel() {

        let level = 0;

        let parent = this.parent;   // start with parent

        while (parent) {            // check value

            level += 1;

            parent = parent.parent; // assign parent

        }

        //console.log('lvl',level);

        return level;

    }

    toString() {

        // console.log('lvl',this.getLevel());

        let prefix = " ".repeat(this.getLevel() * 3);

        prefix += this.getLevel() === 0 ? "" : "|__";

        console.log(prefix + this.index);

        if (this.children) {

            for (let i = 0; i < this.children.length; i++) {

                this.children[i].toString();

            }

        }

    }

    pathToRoot() {

        return 0;

    }

}

const main = (() => {

  let root = new Node('root');

  let kid1 = new Node('kid1');

  let kid2 = new Node('kid2');

  let kid3 = new Node('kid3');

  let kid4 = new Node('kid4');

  root.addChild(kid1);

  kid1.addChild(kid2);

  kid2.addChild(kid3);

  kid3.addChild(kid4);

  console.log('kid4 lvl :', kid4.getLevel())

  root.toString(root);

console.log(root);

})();

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

这似乎与机制无关。你缺少一个基本情况（所以递归函数将永远保持运行）。您需要考虑递归应该在什么情况下结束。this

toString (){

        // think of your base case here. Examples are as below

        // should it be prefix === ""?

        // should it be when length of prefix smaller or greater than specific length 

        let prefix = " ".repeat(this.getLevel()*3);

        prefix += this.getLevel()===0 ? "" :"|__";

        console.log(prefix + this.index);

        if(this.children){

            for(let i = 0; i < this.children.length; i++){

                this.children[i].toString();

            }

        }

    }