What is the output of this code???

Question

alert("john" || "user");
// Answer is john..

alert("john" && "user");
//Answer is user

Does anyone know how the answer came about?

Answer 1

|| and && in JS don't return true or false like other lenguages, but the first value that halts the short-circuit evaluation

That means that || returns the first true value or the last false one

while && returns the first false value or the last true one

Answer 2

Read the following, they helped me understand it.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_AND

Answer 3

https://en.m.wikipedia.org/wiki/Truth_value

https://en.m.wikipedia.org/wiki/Short-circuit_evaluation

Answer 4

S.P. Karthee I took different example

https://code.sololearn.com/WA9VqK0u0FPi/?ref=app

https://code.sololearn.com/WFVrdH9nWD2v/?ref=app

Check this article https://medium.com/@cpenarrieta/javascript-logical-operators-22ec8b5624af

Answer 5

Thx! I got it!

expr1 || expr2
If expr1 can be converted to true, returns expr1; else, returns expr2.

expr1 && expr2
If expr1 can be converted to true, returns expr2; else, returns expr1.

Answer 6

Yes! js is generally a strange language and you need to know its features.

https://www.sololearn.com/post/207103/?ref=app

Answer 7

Thanks 🙂

Answer 8

Sololearn's one of challenge question

Answer 9

Angelo how js determines that John is true in the first alert, and the user is true in the second alert?

Answer 10

Ярослав Вернигора(Yaroslav Vernigora) they are not empty strings

True and false state of variables is not really about truth, it's more about 1s and 0s

Answer 11

I still didn't get it. where can I read about it? carefully study the operation of logical operators?

Answer 12

Guys, js logical operates are different from other languages???

Answer 13

See this link:

https://www.smashingmagazine.com/2011/05/10-oddities-and-secrets-about-javascript/