Question

在没有什么我是新的之前，我很高兴加入这个伟大的社区。问题是，我有一个名为Character的JavaScript类，如下所示：

var Character = function()

{

    // ..Some previous Properties / Methods (included one called "StareDown()")..

    // And this method:

    this.GrabDown = function()

    {
        Context.clearRect(0, 0, CanvasWidth, CanvasHeight);
        //Context.fillRect(0, 0, CanvasWidth, CanvasHeight);
        Context.drawImage(this.GrabbingDown, CharacterX, CharacterY, SpriteWidth, SpriteHeight);

        window.setTimeout
        (
            function()

            {
                // Here is where I want to call the parent class method "StareDown()", but I don't know how.                
            },
            250
        );
    }
}

所以这是我的一个大问题，如何通过该子匿名函数访问父方法？我一直想弄清楚整个晚上，但我找不到一些有用的信息，谢谢！

Answer 1

您需要将父项的this对象存储在变量中（假设您已将函数定义为this.StareDown = function () {...}

var Character = function()

{

    // ..Some previous Properties / Methods (included one called "StareDown()")..
    this.StareDown = function() {...}

    var curCharacter = this;

    this.GrabDown = function()

    {
        Context.clearRect(0, 0, CanvasWidth, CanvasHeight);
        //Context.fillRect(0, 0, CanvasWidth, CanvasHeight);
        Context.drawImage(this.GrabbingDown, CharacterX, CharacterY, SpriteWidth, SpriteHeight);

        window.setTimeout
        (
            function()

            {
                // Here is where I want to call the parent class method "StareDown()", but I don't know how.       
                curCharacter.StareDown(...);         
            },
            250
        );
    }
}

Answer 2

您可以使用window.setTimeout(this.StareDown,250);但请记住，该方法将在全局上下文中调用（即，这将指向window，而不是调用Character的{{1}}实例GrabDown方法。

将该函数用作对象方法：

window.setTimeout((function(that)
{
    return function()
    {
        return that.StareDown();
    }
})(this),250);

应该有效。这可能相当冗长，或许可以查看call，apply，尤其是bind的MDN文档可能会很有用

Answer 3

这就是我要做的事情：

var Character = function () {
    this.GrabDown = function () {
        setTimeout(function () {
            // call this.StareDown in here
        }.bind(this), 250);
    };
};

这是有效的，因为我们将this指针绑定到传递给FunctionExpression的匿名setTimeout。因此，它可以像正常的方法一样使用。

在JavaScript类中调用父方法

3 个答案: