Using exponential notation to prevent rounding errors.js

console.log(Number(Math.round(1.005 + "e2") + "e-2")) // 1.01

const roundAccurately = (number, decimalPlaces) => Number(Math.round(number + "e" + decimalPlaces) + "e-" + decimalPlaces)

console.log(roundAccurately(1.005, 2)) // 1.01

The lower case e is exponential notation, so 10 to the power of positive 2 or minus 2.

Since the built-in rounding function only works on the first decimal place, you can move the decimal point (with the e notation), round, and move the decimal point back.

I'd recommend trying each piece of the code individually, reading the docs on Math.round, and just completely avoiding this use case if it doesn't make sense to you.

Again, the "right" solution here would be to use something more robust. Math.round(1.005) is 1, not 1.01 or 1.0 as you might expect. @y-a11y

@DoctorDerek Thank you so much! This makes a lot more sense now

@hamidgasmi Nope! JavaScript's built-in math isn't great if you actually need precision or are working with exponential notation. I'd recommend using a library. MathJS is a good place to start. https://mathjs.org/

great, thanks.

very helpful.