Javascript未捕获类型错误无法设置未定义的属性 '0'

Question

此代码给出了 UNCAUGHT TYPE ERROR:CANNOT SET PROPERTY '0' OF UNDEFINED(..)为什么会出现这样的错误？

function node() {
    this.parent = null;
    this.children = [];
}
node.prototype.m = function () {
    var insertchild = function (parent, child) {
        var i;
        if (typeof this.children === "undefined")
            i = 0;
        else
            i = this.children.length;
        this.parent = parent;
        this.children[i] = child;
        console.log(parent + " " + child);
    }
    return insertchild;
}
var n = new node();
n.m()('A', 'B');

Answer 1

问题出在 insertchild 函数内的 this

一种解决方案:

function node() {
    this.parent = null;
    this.children = [];
}
node.prototype.m = function() {
    var insertchild = function(parent, child) {
        var i = this.children.length;
        // next four lines are not required
        //if (typeof this.children === "undefined")
        //    i = 0;
        //else
        //    i = this.children.length;
        this.parent = parent;
        this.children[i] = child;
        console.log(parent + " " + child);
    }
    return insertchild.bind(this); // fix is here
}
var n = new node();
n.m()('A', 'B');

如果您处于没有 .bind() 方法的环境中

function node() {
    this.parent = null;
    this.children = [];
}
node.prototype.m = function() {
    var me = this;
    var insertchild = function(parent, child) {
        var i = me.children.length;
        me.parent = parent;
        me.children[i] = child;
        console.log(parent + " " + child);
    }
    return insertchild;
}
var n = new node();
n.m()('A', 'B');

我认为