The tilde(~) operator: the secret weapon for efficient integer conversion

In JavaScript, the tilde (~) is a bitwise NOT operator. It performs a bitwise NOT operation on its operand, which inverts the bits of the operand.

For example:

let x = 5;  // 00000000000000000000000000000101
let y = ~x; // 11111111111111111111111111111010

It's important to note that the bitwise NOT operator only works on integers. If you try to use it on a non-integer value (such as a string or a floating-point number), it will be converted to an integer before the operation is performed.

The tilde operator can also be used as a shorthand for Math.floor() to round a number down to the nearest integer. For example:

let x = 5.7;
let y = ~~x;  // y is 5

In this example, the double tilde operator ~~ rounds the number x down to the nearest integer, resulting in y being set to 5. This is equivalent to using the Math.floor() function.

Just be mindful with the size of your integers using the double NOT operator

// 10 digits
> parseInt(9999999999)
9999999999
> ~~9999999999
1410065407

// 9 digits
> parseInt(999999999)
999999999
> ~~999999999
999999999

Comments

[Zero Dragon]

Just be mindful with the size of your integers using the double NOT operator

// 10 digits
> parseInt(9999999999)
9999999999
> ~~9999999999
1410065407

// 9 digits
> parseInt(999999999)
999999999
> ~~999999999
999999999

But in general I use it when I have to do a simple parseInt from small integers

> ~~'20221220' === 20221220
true

[aniketcodes]

Thanks.Adding this to the post.

[Gil Fewster]

Nice tip. Might be worth noting that it’s not the most well-known operator in the JS universe, so it may reduce the readability of your code.

I’ve seen some approaches which use bitwise NOT but wrap it in a named function so the the purpose in context is clearer to anyone not familiar with the technique.

[aniketcodes]

Yeah. Couldn't agree more on this, but it might be useful to land some good impressions as a coder.