locutus/esm/rust/str/rsplitn.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export function rsplitn(n, delimiter, str) {
    //      discuss at: https://locutus.io/rust/rsplitn/
    // parity verified: Rust 1.85
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Reverse-order variant of splitn.
    //       example 1: rsplitn(3, ' ', 'Mary had a little lamb')
    //       returns 1: ['lamb', 'little', 'Mary had a']
    //       example 2: rsplitn(2, '::', 'lion::tiger::leopard')
    //       returns 2: ['leopard', 'lion::tiger']
    //       example 3: rsplitn(3, 'X', 'lionXXtigerXleopard')
    //       returns 3: ['leopard', 'tiger', 'lionX']
    const limit = Math.trunc(Number(n));
    if (!Number.isFinite(limit) || limit <= 0) {
        return [];
    }
    const source = String(str);
    const value = String(delimiter);
    if (limit === 1) {
        return [source];
    }
    if (value === '') {
        const parts = ['', ...Array.from(source), ''].reverse();
        if (parts.length <= limit) {
            return parts;
        }
        return [
            ...parts.slice(0, limit - 1),
            parts
                .slice(limit - 1)
                .reverse()
                .join(''),
        ];
    }
    const out = [];
    let remainder = source;
    for (let i = 0; i < limit - 1; i += 1) {
        const index = remainder.lastIndexOf(value);
        if (index < 0) {
            break;
        }
        out.push(remainder.slice(index + value.length));
        remainder = remainder.slice(0, index);
    }
    out.push(remainder);
    return out;
}