Javascript keydown 操作对象

Question

我正在尝试创建一个对象来处理用户的键盘输入。

var control = new Control ();

function Control () {
    this.w = 0;
    this.a = 0;
    this.s = 0;
    this.d = 0;
    document.addEventListener("keydown", this.KeyDown);
    document.addEventListener("keyup", this.KeyUp);
}
Control.prototype.KeyDown = function (event, control) {
    switch (event.keyCode) {
        case 87:
            this.w = 1;
            break;
        case 65:
            this.a = 1;
            break;
        case 83:
            this.s = 1;
            break;
        case 68:
            this.d = 1;
            break;
    }
    console.log("w: " + this.w + "\na: " + this.a + "\ns: " + this.s + "\nd: " + this.d);
}
Control.prototype.KeyUp = function (event) {
    switch (event.keyCode) {
        case 87:
            this.w = 0
            break;
        case 65:
            this.a = 0;
            break;
        case 83:
            this.s = 0;
            break;
        case 68:
            this.d = 0;
            break;
    }
    console.log("w: " + this.w + "\na: " + this.a + "\ns: " + this.s + "\nd: " + this.d);
}

问题是，每当我在“keyDown”和“keyUp”函数中写入“this”时，“this”指的是文档，而不是“control”对象。如何从函数内访问“控制”对象？

Answer 1

1. this.KeyDown,this.KeyUp 将在 Control 构造函数中为 undefined，您需要移动 var control = new Control (); 最后。

2. 您可以使用以下代码绑定(bind)control上下文。

   document.addEventListener("keydown", this.KeyDown.bind(this)); document.addEventListener("keyup", this.KeyUp.bind(this));

注意:IE8 不支持绑定(bind)，替代方案是 here