“this”在回调函数后指向窗口而不是我的原型函数

Question

我有这个原型功能

(function(window, undefined){
    function Waypoint (el, callback, offset){
        this.el = el;
        this.cb = callback;
        this.offset = offset || 0;
        window.optimizedScroll.add(this.passedWaypoint);
        //window.optimizedScroll.add(this.passedWaypoint.call(this)); doesn't work
    }

    Waypoint.prototype.passedWaypoint = function(){
        //if element passes a point execute the callback function
        //this.cb(); //undefined
        console.log(this);  //refers to window and not to my obj
    };

    window.Waypoint = Waypoint;

})(this); 

var myElement1 = new Waypoint("myElement", function(){
    console.log("i have traveled so far");
});

从这个页面优化滚动 https://developer.mozilla.org/en-US/docs/Web/Events/resize（我只改变了滚动调整大小）

var optimizedScroll = (function(window, undefined) {
    var callbacks = [], running = false;
    // fired on resize event
    function scroll() {
        if (!running) {
            running = true;
            window.requestAnimationFrame(runCallbacks);
        }
    }
    // run the actual callbacks
    function runCallbacks() {
        callbacks.forEach(function(callback) {
            callback(); 
        });
        running = false; 
    }
    // adds callback to loop
    function addCallback(callback) {
        if (callback) {
            callbacks.push(callback);
        }
    }
    return {
        // public method to add additional callback
        add: function(callback) {
            if (!callbacks.length) {
                window.addEventListener('scroll', scroll);
            }
            addCallback(callback);
        }
    };
})(this);

当我滚动时回调函数被执行，但我对“this”这个小字有疑问。我怎样才能实现“this”指的是我的 obj 而不是窗口。我玩过“呼叫”，但我没听懂...

格雷戈

Answer 1

@MysterX 的评论是正确的 ;)

window.optimizedScroll.add(this.passedWaypoint.bind(this));

不是“调用”我尝试过的东西

谢谢！ ;)