Can (a== 1 && a ==2 && a==3) ever evaluate to true?

2018-05-31 23:25:26

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Is it ever possible that (a== 1 && a ==2 && a==3) could evaluate to true in JavaScript?

This is an interview question asked by a major tech company. It happened two weeks back, but I'm still trying to find the answer. I know we never write such code in our day-to-day job, but I'm curious.

如果您充分利用==工作原理，可以简单地使用自定义的toString （或valueOf ）函数创建一个对象，该对象每次使用时都会改变其返回的内容，以满足所有三个条件。

const a = {
  i: 1,
  toString: function () {
    return a.i++;
  }
}

if(a == 1 && a == 2 && a == 3) {
  console.log('Hello World!');
}

我无法抗拒 - 其他答案无疑是真实的，但你真的不能走过以下代码：

var aﾠ = 1;
var a = 2;
var ﾠa = 3;
if(aﾠ==1 && a== 2 &&ﾠa==3) {
    console.log("Why hello there!")
}

有可能的！

var i = 0;

with({
  get a() {
    return ++i;
  }
}) {
  if (a == 1 && a == 2 && a == 3)
    console.log("wohoo");
}

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