Question

我有这段代码：

function Tree() {
    this.capacity = 1;
    this.contents = 0;
    this.children = [];
    this.divided = false;

    this.pour = function(amount) {
        this.contents += amount;
        if (this.contents <= 1) {
            return;
        }

        if (!this.divided) {
            this.divide();
        }
        amount = this.contents - 1;
        this.contents = 1;
        for (let child in this.children) {
            this.children[child].pour(amount * .5);
        }
    }

    this.divide = function() {
        this.children = new Array(2).fill(0).map(x => new Tree());
        this.divided = true;
        return;
    }

    this.getContents = function(row, currentRow) {
        if (currentRow === undefined) {
            currentRow = 0;
        }

        if (row === currentRow) {
            console.log('Contents:', this.contents)
            return this.contents;
        }

        if (this.divided) {
            console.log(row, currentRow)
            currentRow++;
            this.children[0].getContents(row, currentRow);
        } else {
            return;
        }
    }
}

创建一棵树，倒入其中，并使用以下内容获取其内容：

let tree = new Tree();
tree.pour(10);
tree.getContents(1);

它应返回1，因为第二行内容为1.它在控制台中记录1，但不返回正确的值。我很好奇出了什么问题。

编辑：我看着将它切换到一个类并且它没有解决问题：

class Tree {
    constructor() {
        this.capacity = 1;
        this.contents = 0;
        this.children = [];
        this.divided = false;
    }

    pour(amount) {
        this.contents += amount;
        if (this.contents <= 1) {
            return;
        }

        if (!this.divided) {
            this.divide();
        }
        amount = this.contents - 1;
        this.contents = 1;
        for (let child in this.children) {
            this.children[child].pour(amount * .5);
        }
    }

    divide() {
        this.children = new Array(2).fill(0).map(x => new Tree());
        this.divided = true;
        return;
    }

    getContents(row, currentRow) {
        if (currentRow === undefined) {
            currentRow = 0;
        }

        if (row === currentRow) {
            console.log('Contents:', this.contents)
            return this.contents;
        }

        if (this.divided) {
            console.log(row, currentRow)
            currentRow++;
            this.children[0].getContents(row, currentRow);
        } else {
            return;
        }
    }
}

Answer 1

您看到的console.log是此次通话的结果：

 if (this.divided) {
        console.log(row, currentRow)
        currentRow++;
        this.children[0].getContents(row, currentRow); //<-- here
        // this is calling getContents() but ignores the return value

但是在这种情况下你实际上并没有返回任何内容，因此内部console.log()会触发，但返回值是未定义的。

我不确定代码应该做什么，但是当满足条件时返回一个值会导致整个函数的返回值：

if (this.divided) {
        console.log(row, currentRow)
        currentRow++;
        return this.children[0].getContents(row, currentRow);

Answer 2

它将1记录到控制台，因为您调用了

results

当前行未定义，因为您未在参数

中传递它

tree.pour(10)

所以它意味着currentRow为0而row（1）不等于currentRow（0），这就是它返回undefined的原因。

if (currentRow === undefined) {
        currentRow = 0;
    }

    if (row === currentRow) {
        console.log('Contents:->', this.contents)
        return this.contents;
    }

在Javascript中返回对象属性未定义

2 个答案: