19 lines
858 B
TypeScript
19 lines
858 B
TypeScript
/**
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* Format large numbers in compact form: K (thousands), M (millions), B (billions).
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* e.g. 1500 → "1.5K", 1_200_000 → "1.2M", 999 → "999"
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*/
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export function formatCompact(n: number): string {
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if (!Number.isFinite(n) || n < 0) return "0";
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const fmt = (v: number) =>
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v % 1 === 0 ? v.toFixed(0) : v.toFixed(1).replace(/\.0$/, "");
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// `toFixed(1)` can round up to 1000 at the top of a band (e.g. 999_999 / 1e3
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// -> "1000.0"), which would render a non-compact "1000K"/"1000M". Promote to
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// the next unit in that case so the output stays compact.
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if (n >= 1e9) return fmt(n / 1e9) + "B";
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if (n >= 1e6)
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return n / 1e6 >= 999.95 ? fmt(n / 1e9) + "B" : fmt(n / 1e6) + "M";
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if (n >= 1e3)
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return n / 1e3 >= 999.95 ? fmt(n / 1e6) + "M" : fmt(n / 1e3) + "K";
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return n.toLocaleString(undefined, { maximumFractionDigits: 0 });
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}
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