Don't use regex that can be slow

[tats-u]

The regex introduced in #289 can be slow.
For example,

('a' + ' '.repeat(65534) + 'a').replace(/^[\t \r\n]+|[\t \r\n]+$/g,"").length

takes a long time to be done. (a few seconds)

/^[\t \r\n]+(?![\t \r\n])|(?<![\t \r\n])[\t \r\n]+$/g,

fixes the problem, but the naive implementation of this PR seems to be faster than it when the number of trimmed spaces are not many according to my private bench by mitata.
Using charCodeAt is fastest but reduces the explainability due to the raw code point number literals (e.g. 0x20 for " ").
Sorry for having submitted problematic code.

import { run, bench, boxplot } from "mitata";

const PAD = " \n".repeat(16777216)
const PAD2 = " \n\t".repeat(1024)
const CH = "abc".repeat(16777216)
const DATA = `${PAD2}${CH}${PAD}${CH}${PAD2}`

export function useIfFn(str) {
    let start = 0;
    for(; start < str.length; start++) {
        if (!isSpace(str[start])) {
            break;
        }
    }
    let end = str.length - 1;
    for(; end >= start; end--) {
        if (!isSpace(str[end])) {
            break;
        }
    }
    return str.slice(start, end + 1);

    function isSpace(c) {
        return c === " " || c === "\t" || c === "\n" || c === "\r";
    }
}

export function useIfFnCc(str) {
    let start = 0;
    for(; start < str.length; start++) {
        if (!isSpace(str.charCodeAt(start))) {
            break;
        }
    }
    let end = str.length - 1;
    for(; end >= start; end--) {
        if (!isSpace(str.charCodeAt(end))) {
            break;
        }
    }
    return str.slice(start, end + 1);

    function isSpace(c) {
        return c === 0x20 || c === 0x09 || c === 0x0a || c === 0x0d;
    }
}
export function useRegex(str) {
    return str.replace(/^[ \t\n]+(?![ \t\n])|(?<![ \t\n])[ \t\n]+$/g, "");
}


boxplot(() => {
    bench("useIfFn", () => {
        useIfFn(DATA);
    });
    bench("useRegex", () => {
        useRegex(DATA);
    });
    bench("useIfFnCc", () => {
        useIfFnCc(DATA);
    });
});

await run();

clk: ~4.33 GHz
cpu: 13th Gen Intel(R) Core(TM) i7-1355U
runtime: node 22.12.0 (x64-win32)

benchmark              avg (min … max) p75   p99    (min … top 1%)
-------------------------------------- -------------------------------
useIfFn                  10.54 µs/iter   9.90 µs █
                 (8.80 µs … 419.80 µs)  37.40 µs █▇▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
useRegex                106.56 ms/iter 107.16 ms       █   ▃
               (101.05 ms … 115.18 ms) 110.98 ms ▆▁▁▁▆▁█▁▁▁█▆▆▁▁▁▁▁▁▆▁
useIfFnCc                 9.94 µs/iter   8.80 µs █
                 (7.10 µs … 200.50 µs)  47.80 µs █▇▆▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁

                        ┌                                            ┐
                        ┬
                useIfFn │
                        ┴
                                                                 ╷┌┬ ╷
               useRegex                                          ├┤│─┤
                                                                 ╵└┴ ╵
                        ┬
              useIfFnCc │
                        ┴
                        └                                            ┘
                        7.10 µs           55.49 ms           110.98 ms

[jgm]

Thanks! useIfFnCc looks good. Perhaps add a comment on isSpace to indicate that 0x20 = space, etc.
Want to make a PR?

[tats-u]

I did. It looks like you prefer the "Rebase and Merge" strategy, so I amended the commit and did a force-push.

[tats-u]

let → var

[tats-u]

Improved the comment.

[jgm]

Thanks!