JS: TypeError: this._init is not a function. (In 'this._init()', 'this._init' is undefined)

Question

也许你会发现问题所在。控制台总是说：

TypeError: this._init 不是函数。（在'this._init()'中，'this._init'未定义）

nodes = [];
for (var i = 0; i < 3; i++) {
    var newNode = new Node(i*100,0);
    nodes.push(newNode);
};

function Node(posX, posY, parent) {
    if (typeof parent === 'undefined') { parent = 0; }
    this.parent = parent;
    this.children = [];
    this.text = "Node";
    this.posX = posX;
    this.posY = posY;
    this._init();

    this._init = function() {
        alert("test");
    }
}

Answer 1

看起来你在定义它之前调用了 _init。

this._init = function() {
   alert('test');
}

this._init();

Answer 2

您需要在调用之前定义函数：

function Node(posX, posY, parent) {
    if (typeof parent === 'undefined') { parent = 0; }
    this.parent = parent;
    this.children = [];
    this.text = "Node";
    this.posX = posX;
    this.posY = posY;

    this._init = function() {
        alert("test");
    }

    this._init();   
}

http://jsfiddle.net/4wsLhd8y/

如果您在别处定义函数之前调用过函数，您可能会对此感到困惑。在某些情况下，您的功能可能是 "hoisted" 到你的脚本的顶部。下面是一个完全合法的调用：

isItHoisted();

function isItHoisted() {
    console.log("Yes!");
}

http://adripofjavascript.com/blog/drips/variable-and-function-hoisting

您现在可能已经知道，对象上的方法函数没有提升，所以您会看到您看到的错误。

JS: TypeError: this._init is not a function. (In 'this._init()', 'this._init' is undefined)

JS: TypeError: this._init is not a function. (In 'this._init()', 'this._init' is undefined)

javascript

oop

class

typeerror