30-seconds-of-code: Round Number To n Digits

[ecwyne]

Wanted to gauge interest before creating a PR. Would others consider this clear & useful?

const round = (n, decimals = 0) => Number(`${Math.round(`${n}e${decimals}`)}e-${decimals}`)

Importantly the above works correctly with all floating point numbers.

// All of the following *should* return 1.01 but *actually* return 1

Number(1.005.toFixed(2))
Math.round(1.005 * 100) / 100

[Chalarangelo]

Hi, thanks for the interest! I like the idea, was planning to add something like what is mentioned on this SO thread. Basically, round the number only if necessary and omit trailing zeroes. Do you think you can code that, so we can add it?

[ecwyne]

Of course @Chalarangelo!

The current implementation has the type signature (Number, Number?) => Number so it already only rounds if necessary and omits trailing zeroes (Numbers don't have trailing zeroes)

If you wanted (Number, Number?) => String you can easily just call .toString() on the result

[Chalarangelo]

@ecwyne get cracking, we should get this added! 😉

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