Round to a number of digits

Apply decimal scaling and JavaScript rounding for display-oriented values.

JavaScript Version 1.0.0 · MIT · .md

function roundTo({ value, digits }) { const factor = 10 ** digits; return Math.round(value * factor) / factor; }

Input & expected output

{
  "value": 12.3456,
  "digits": 2
}

12.35

The edge case

{
  "value": 1.005,
  "digits": 2
}

1

Know the limits

• Binary floating-point explains the 1.005 edge case. This is not exact decimal arithmetic.
• The lab allows 0–6 digits. Never use this function as a financial rounding policy.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Clamp a number to a range — Keep a number inside an inclusive minimum and maximum.
• Add an ordinal suffix to a number — Append st, nd, rd or th to a positive integer.
• Calculate Fibonacci numbers — Return the nth Fibonacci number with memoized recursion.