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Can (aﾠ == 1 && a == 2 && ﾠa == 3) equal true?

Karolis Ramanauskas on April 21, 2018

Here is a JavaScript trivia question. Can the expression (aﾠ == 1 && a == 2 && ﾠa == 3) ever evaluate to true? Well, today I foun...

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J. Pichardo • May 31 '18 • Edited

Nice post, I wouldn't have thought about using an "invisible" character.

Now, for the curious people, there is also another way :)



const a = {
  valueOf: (function(){
      let x = 1;
      return () => x++;
    })()
}

console.log(a == 1 && a == 2 && a == 3); // => true

Just for reference, the concepts used here are type coercion, closures and immediate function invocation.

Regards

p.s. can a === 1 && a === 2 && a === 3 evaluate to true?

Junyoung Clare Jang • Jun 2 '18

Yes, you also can make true from a === 1 && a === 2 && a === 3 without invisible character, since, we have getter.

let i = 0;
Object.defineProperty(window, 'a', {
  get: function() {
    return ++i;
  }
});
console.log(a === 1 && a === 2 && a === 3);

J. Pichardo • Jun 2 '18

Precisely, nice catch.

Karolis Ramanauskas • May 31 '18

Nice, interesting approach!

Henrique Marques • Jun 4 '18

Nice! Way more useful and interesting than the actual post.

Nested Software • May 31 '18

This is very cool and scary!

Eric Keyte • Jun 3 '18

This feels a little clickbait-y. It feels the same as photographing two glasses of water after 3 hours in the freezer, and then saying, “we put two glasses of water in the freezer and one of them didn’t freeze!” And then revealing that one glass was actually full of vodka.

I don’t want to try to misunderstand the spirit of this article, but I don’t get why any of this is relevant.