Ghost: Skill for Claude Code

Format Numbers

When editing .tsx files, ensure all user-facing numbers are formatted using the formatNumber utility from @tryghost/shade/utils.

Import

import { formatNumber } from '@tryghost/shade/utils';

When to use formatNumber

Use formatNumber() when rendering any numeric value that is displayed to the user, including:

• Member counts, visitor counts, subscriber counts
• Email engagement metrics (opens, clicks, bounces)
• Revenue amounts (combine with centsToDollars() for monetary values)
• Post analytics (views, link clicks)
• Any count or quantity shown in UI

Correct usage

<span>{formatNumber(totalMembers)}</span>
<span>{formatNumber(link.count || 0)}</span>
<span>{`${currencySymbol}${formatNumber(centsToDollars(mrr))}`}</span>
<span>{post.members > 0 ? `+${formatNumber(post.members)}` : '0'}</span>

Antipatterns to avoid

Do NOT use any of these patterns for formatting numbers in TSX files:

// BAD: raw .toLocaleString()
<span>{count.toLocaleString()}</span>

// BAD: manual Intl.NumberFormat
<span>{new Intl.NumberFormat('en-US').format(count)}</span>

// BAD: raw number without formatting
<span>{memberCount}</span>

// BAD: manual regex formatting
<span>{count.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',')}</span>

Related utilities

• formatPercentage() - for percentages (e.g., open rates, click rates)
• abbreviateNumber() - for compact notation (e.g., 1.2M, 50k)
• centsToDollars() - convert cents to dollars before passing to formatNumber

All are imported from @tryghost/shade/utils.