本文详细介绍了JavaScript中对象在不同上下文中如何被转换为布尔值、字符串和数值。当对象用于布尔上下文时，非空对象转换为true；在字符串上下文中，通过调用对象的toString()方法来获取其字符串表示形式；而在数值上下文中，则先尝试调用valueOf()方法获取原始值，若该方法返回对象本身，则进一步使用toString()方法将其转换为字符串，并最终将该字符串转换为数值。
[size=medium]When a non-null object is used in a Boolean context, it converts to true . When an object is used in a
string context, JavaScript calls the toString( ) method of the object and uses the string value returned
by that method. When an object is used in a numeric context, JavaScript first calls the valueOf( ) method
of the object. If this method returns a primitive value, that value is used. In most cases, however, the
valueOf( ) method returns the object itself. In this case, JavaScript first converts the object to a string
with the toString( ) method and then attempts to convert the string to a number.[/size]
string context, JavaScript calls the toString( ) method of the object and uses the string value returned
by that method. When an object is used in a numeric context, JavaScript first calls the valueOf( ) method
of the object. If this method returns a primitive value, that value is used. In most cases, however, the
valueOf( ) method returns the object itself. In this case, JavaScript first converts the object to a string
with the toString( ) method and then attempts to convert the string to a number.[/size]
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