locutus/esm/tcl/string/last.js

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

export function last(needle, haystack, lastIndex) {
    //      discuss at: https://locutus.io/tcl/last/
    // parity verified: Tcl 8.6
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //       example 1: last('or', 'Hello World')
    //       returns 1: 7
    //       example 2: last('l', 'Hello World')
    //       returns 2: 9
    //       example 3: last('l', 'Hello World', 3)
    //       returns 3: 3
    const source = String(haystack);
    const search = String(needle);
    if (search === '') {
        if (lastIndex === undefined) {
            return source.length;
        }
        return Math.min(Math.max(0, Math.trunc(Number(lastIndex))), source.length);
    }
    if (lastIndex === undefined) {
        return source.lastIndexOf(search);
    }
    return source.lastIndexOf(search, Math.trunc(Number(lastIndex)));
}