AddThisFeature

Number Formatting Component

Format every count, percentage, and total the same way, without rounding away meaning.

moderate User Experience

What it adds

One shared path for displaying numeric values, covering precision, abbreviation, locale separators, and the values that are not numbers.

What your agent is told to do

5
  1. 1

    Find every numeric value the app renders — counts, totals, percentages, durations, file sizes, ratios — and give each a declared type so the display rules follow from what the number is rather than from where it appears.

  2. 2

    Set precision per type and never abbreviate a value the user must act on. A summary tile can say 1.2k, but a quantity someone is about to reconcile or pay must show in full.

  3. 3

    Keep the exact value available even where a shortened one is displayed, on hover and to assistive technology, so a rounded figure can always be checked.

  4. 4

    Format separators, decimal marks, and percentage placement from the viewer's locale rather than hardcoding a convention, and align numeric columns on the decimal so magnitudes can be compared down a column.

  5. 5

    Do not sort or filter on the formatted string. An abbreviated or separated value sorts as text, which puts 9 after 1.2k; keep the raw number for every comparison and use the formatted form only for display.

Edge cases it handles

7
  • Rounding must not change what the number means. A 99.6 per cent success rate displayed as 100 per cent hides every failure, so round toward the honest side for values where the difference matters.
  • The value used for sorting, filtering, and thresholds must be the raw number, never the rendered string.
  • Separators and decimal marks differ by locale — the same characters mean opposite things in different regions — so they must come from the viewer's locale rather than the developer's.
  • Null, infinity, not-a-number, and negative zero each need a defined rendering. A missing value shown as 0 is a false statement about the data, and negative zero must display as zero.
  • Very large and very small values need a defined ceiling and floor rather than an unbounded string that breaks the column width.
  • A percentage must be unambiguous about whether it is already scaled; a ratio of 0.5 rendered as 0.5 per cent is a hundredfold error.
  • Dates, times, and durations expressed as timestamps belong to Date and Time Display Component; this component owns quantities only.

Definition of done

9
  • Every numeric display in the app goes through the shared formatting path with a declared value type.
  • Precision and abbreviation rules are defined per type and applied consistently.
  • Sorting, filtering, and comparison always use the raw value, never the formatted string.
  • Separators and decimal marks follow the viewer's locale.
  • Null, infinity, not-a-number, and negative zero each render a defined state.
  • The exact value is reachable wherever an abbreviated or rounded one is shown.
  • Numeric columns align on the decimal point.
  • The feature matches the existing design system.
  • No existing functionality is broken.

Related features

How it works

  1. 1

    Copy the link

    Grab the Markdown instruction URL for this feature.

  2. 2

    Give it to your AI

    Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.

  3. 3

    It inspects, then implements

    Your agent reads your existing app first, then adds the feature to fit it.

Works with your stack

These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.

Need it tighter than that? Customize the feature and tell it exactly what you're running.