查询不存在的属性并不总是会引发错误

Question

为什么在执行这段代码时，只检查thisThrowsError实际上是否会抛出错误，但查询原型对象或this上下文中不存在的属性不会？

function Test()
{

    if(this.someVar){}
    if(Test.prototype.someVar){}  
    if(thisThrowsError){}
 }

var test = new Test();

Answer 1

请参阅：Why does an undefined variable in Javascript sometimes evaluate to false and sometimes throw an uncaught ReferenceError?