警告 - 危险地使用全局 this 对象?

WARNING - dangerous use of the global this object?

Google 闭包编译器抱怨这段代码:

function Message() {
    this.message = "";
    this.nickname = "";
    this.time = 0;
    this.my = false;
};

这里有什么危险?它应该如何创建 "objects"?现在我做

var m = new Message();

获取 "type" 消息的初始化对象。

尝试注释代码以告诉编译器这是一个构造函数:

/**
 * A message
 * @constructor
 */
function Message() {
    this.message = "";
    this.nickname = "";
    this.time = 0;
    this.my = false;
};

https://developers.google.com/closure/compiler/docs/js-for-compiler#overview