locutus/esm/rust/str/split_once.js

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

export function split_once(delimiter, str) {
    //      discuss at: https://locutus.io/rust/split_once/
    // parity verified: Rust 1.85
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Splits string on first delimiter occurrence and returns [left, right] or null.
    //       example 1: split_once('=', 'a=b=c')
    //       returns 1: ['a', 'b=c']
    //       example 2: split_once('::', 'x::y')
    //       returns 2: ['x', 'y']
    //       example 3: split_once(':', 'abc')
    //       returns 3: null
    const haystack = String(str);
    const needle = String(delimiter);
    if (needle === '') {
        return ['', haystack];
    }
    const index = haystack.indexOf(needle);
    if (index < 0) {
        return null;
    }
    return [haystack.slice(0, index), haystack.slice(index + needle.length)];
}