locutus/powershell/string/substring.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.substring = substring;
function substring(str, startIndex, length) {
    //      discuss at: https://locutus.io/powershell/substring/
    // parity verified: PowerShell 7.4
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //       example 1: substring('Hello World', 6)
    //       returns 1: 'World'
    //       example 2: substring('Hello World', 0, 5)
    //       returns 2: 'Hello'
    //       example 3: substring('abcdef', 2, 2)
    //       returns 3: 'cd'
    const source = String(str);
    const start = Math.trunc(Number(startIndex));
    if (!Number.isFinite(start) || start < 0 || start > source.length) {
        throw new RangeError('substring(): startIndex out of range');
    }
    if (length === undefined) {
        return source.slice(start);
    }
    const count = Math.trunc(Number(length));
    if (!Number.isFinite(count) || count < 0 || start + count > source.length) {
        throw new RangeError('substring(): length out of range');
    }
    return source.slice(start, start + count);
}