mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-02 07:43:42 +08:00
Chris Tate
cb572a7b67
`toUpperCase` and `toLowerCase` now record that a result of their ASCII path is ASCII. `padStart` and `padEnd` take the UTF-16 lengths of the receiver and the fill the way `length` does: a proven-ASCII or short string is counted directly instead of claiming a string-index entry. A one-unit fill repeats without a division, a one-byte fill with memset, and a result padded from an ASCII receiver and fill is recorded as ASCII. `word.slice(0, 3).toUpperCase().padStart(4, "-")` previously built an index entry for the three-byte receiver on every call.
40 lines
1.4 KiB
TypeScript
40 lines
1.4 KiB
TypeScript
// padStart and padEnd on the results of case conversion and slicing, with
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// ASCII and non-ASCII receivers and fills, and index reads of the results.
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const words = ["alpha", "beta", "gamma", "Delta", "épée", "straße", "日本語", "a😀b"];
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const fills = ["-", "ab", "é", "😀", "", " "];
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function describe(s: string): string {
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return [
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JSON.stringify(s),
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s.length,
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s.charAt(1),
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s.at(-1),
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s.indexOf("A"),
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s.slice(1, 4),
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s.charCodeAt(s.length - 1),
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s.codePointAt(0),
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].join(" ");
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}
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for (const word of words) {
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const upper = word.slice(0, 3).toUpperCase();
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const lower = word.toLowerCase();
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for (const fill of fills) {
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console.log(describe(upper.padStart(6, fill)));
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console.log(describe(lower.padEnd(9, fill)));
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}
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console.log(describe(upper.padStart(2)), describe(upper.padEnd(5)));
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}
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// The same string padded again, compared and used as a key.
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const counts = new Map<string, number>();
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for (let i = 0; i < 40; i++) {
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const key = words[i % words.length]!.slice(0, 3).toUpperCase().padStart(4, "-");
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counts.set(key, (counts.get(key) ?? 0) + 1);
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}
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console.log([...counts].map(([k, v]) => `${k}=${v}`).join(","));
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const padded = "abc".toUpperCase().padStart(5, "😀");
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console.log(padded.length, [...padded].length, padded === "\ud83dABC".padStart(5, "😀"));
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console.log("x".toUpperCase().padEnd(4, "é").normalize("NFD").length);
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