0

What does !+ (exclamation mark addition) mean in JavaScript?

Why is !+"000" true?
Why is !+"0010" false?

Tries:

!+"000" // true !+"00010" // false !+"0a0" // true !+"0,0" // true !+[0,0,0] // true !+[0,1,0] // true true+"000" // true000

I've tried to search:

Here I saw the code: JS - Check if string contain only 0

This information is hard to find on the Internet.

Improve this question
3
  • 1
    It's two separate unary operators Commented Dec 13, 2021 at 16:09
  • 1
    See What does this symbol mean in JavaScript? and the documentation on MDN about expressions and operators and statements. Operators can be combined. You wouldn’t ask about every possible combination, right? Commented Dec 13, 2021 at 16:11
  • 1
    true + "000" doesn’t use the unary +, but the binary one. The specification explains in detail what it does. Commented Dec 13, 2021 at 16:15

1 Answer 1

Reset to default
2

+ is unary plus. It'll convert the expression that follows to a number.

Then, ! negates the expression that follows: if it's truthy, the result is false. If it's falsey, the result is true.

A couple of examples:

!+"000" !0 // because '000', when converted to a number, is 0 true !+"00010" !10 // because "00010", when converted to a number, is 10 false // because 10 is truthy !+[0,1,0] !NaN // because arrays can't be converted to numbers directly (usually) true
Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.