locutus/esm/tcl/string/trimleft.js

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

const escapeForCharClass = (chars) => chars.replace(/[\\\]^/-]/g, '\\$&');
export function trimleft(str, chars) {
    //      discuss at: https://locutus.io/tcl/trimleft/
    // parity verified: Tcl 8.6
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //       example 1: trimleft('  hello  ')
    //       returns 1: 'hello  '
    //       example 2: trimleft('__hello__', '_')
    //       returns 2: 'hello__'
    const value = String(str);
    if (chars === undefined) {
        return value.trimStart();
    }
    if (chars === '') {
        return value;
    }
    const escaped = escapeForCharClass(chars);
    const pattern = new RegExp(`^[${escaped}]+`, 'g');
    return value.replace(pattern, '');
}