javascript - 查询不存在的属性并不总是抛出错误

Question

为什么在执行这段代码时，仅检查 thisThrowsError 实际上会抛出错误，但查询原型(prototype)对象或 this 上下文上不存在的属性却不会？

function Test()
{

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

var test = new Test();

Answer 1

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