javascript - phonegap index.js文件为什么app.receivedEvent不是this.receivedEvent

有人可以告诉我为什么在下面的代码中使用app.receivedEvent('deviceready')而不使用this.receivedEvent('deviceready')吗？

var app = {
    // Application Constructor
    initialize: function() {
        this.bindEvents();
    },
    // Bind Event Listeners
    //
    // Bind any events that are required on startup. Common events are:
    // 'load', 'deviceready', 'offline', and 'online'.
    bindEvents: function() {
        document.addEventListener('deviceready', this.onDeviceReady, false);
    },
    // deviceready Event Handler
    //
    // The scope of 'this' is the event. In order to call the 'receivedEvent'
    // function, we must explicitly call 'app.receivedEvent(...);'
    onDeviceReady: function() {
        app.receivedEvent('deviceready');
    },
    // Update DOM on a Received Event
    receivedEvent: function(id) {
        var parentElement = document.getElementById(id);
        var listeningElement = parentElement.querySelector('.listening');
        var receivedElement = parentElement.querySelector('.received');

        listeningElement.setAttribute('style', 'display:none;');
        receivedElement.setAttribute('style', 'display:block;');

        console.log('Received Event: ' + id);
    }
};

最佳答案

注释实际上解释了在app上使用this的原因：

// The scope of 'this' is the event. In order to call the 'receivedEvent'
// function, we must explicitly call 'app.receivedEvent(...);'

基本上，事件处理程序将使用其自己的this上下文（其中this是事件对象）来调用事件回调。

方法receivedEvent是在app中定义的，而不是在this中定义的（设置为事件回调函数中的事件对象）。在这种情况下，要调用receivedEventil，您可以将其作为包含对象app的方法来调用：

app.receivedEvent(...);

关于javascript - phonegap index.js文件为什么app.receivedEvent不是this.receivedEvent，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/43501360/