locutus/awk/builtin/substr.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.substr = substr;
function substr(str, start, len) {
    //      discuss at: https://locutus.io/awk/substr/
    // parity verified: GNU AWK 5.3
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: AWK uses 1-based indexing, so start=1 is the first character
    //       example 1: substr('hello', 2, 3)
    //       returns 1: 'ell'
    //       example 2: substr('hello', 1, 2)
    //       returns 2: 'he'
    //       example 3: substr('hello', 3)
    //       returns 3: 'llo'
    if (str === undefined || str === null) {
        return '';
    }
    const s = String(str);
    // AWK uses 1-based indexing
    const startIdx = Math.max(0, start - 1);
    if (len === undefined) {
        return s.substring(startIdx);
    }
    return s.substring(startIdx, startIdx + len);
}