以下js代码片段之间的区别

Question

我是Javascript新手，对以下代码片段之间的区别感到困惑。

片段1：

window.onload = function() { 
    var friendlyChat = new FriendlyChat(); 
}; 

片段2：

window.onload = function() { 
    window.friendlyChat = new FriendlyChat(); 
}; 

谁能请告诉他们有什么区别？

Answer 1

片段1：

window.onload = function() { 
    var friendlyChat = new FriendlyChat(); 
}; 

var sample = function() { 
    var sampleInstance = friendlyChat; //error 
    // friendlyChat cannot be accesses here as you have declared it 
    // at function scope which gets destroyed once the function has 
    // returned or completed the execution. 
} 

friendlyChat是局部变量并且可以此函数内部仅访问。

片段2：

window.onload = function() { 
    window.friendlyChat = new FriendlyChat(); 
}; 

var sample = function() { 
    var sampleInstance = friendlyChat; 
    // friendlyChat can be accesses here as you have declared it at 
    // windows scope which is available globally. 
} 

friendlyChat是一个全局变量，因为它已经在根级别即窗口被宣布可以在任何地方访问。