A hubot script that grabs and displays the latest jstip from https://github.com/loverajoel/jstips.
See src/jstips.coffee for full documentation.
In hubot project repo, run:
npm install hubot-jstips --save
Then add hubot-jstips to your external-scripts.json:
["hubot-jstips"]user1>> hubot jstip
hubot>>
#18 - Rounding the fast way
2016-01-18 by pklinger
Today's tip is about performance. Ever came across the double tilde ~~ operator? It is sometimes also called the double NOT bitwise operator. You can use it as a faster substitute for Math.floor(). Why is that?
One bitwise shift ~ transforms the 32 bit converted input into -(input+1). The double bitwise shift therefore transforms the input into -(-(input + 1)+1) making it a great tool to round towards 0. For numeric input, it therefore mimics the Math.ceil() for negative and Math.floor() for positive input. On failure, 0 is being returned, which might come in handy sometimes instead of Math.floor() return value NaN on failure.
// single ~
console.log(~1337) // -1338
// numeric input
console.log(~~47.11) // -> 47
console.log(~~-12.88) // -> -12
console.log(~~1.9999) // -> 1
console.log(~~3) // -> 3
// on failure
console.log(~~[]) // -> 0
console.log(~~NaN) // -> 0
console.log(~~null) // -> 0
// greater than 32 bit integer fails
console.log(~~(2147483647 + 1) === (2147483647 + 1)) // -> 0
Although ~~ may perform better, for the sake of readability please use Math.floor().