url-file-size/index.js

Get file size by URL without downloading it

const https = require('https');
const http = require('http');
const { URL } = require('url');

/**
 * Get file size from URL (in bytes) without downloading it.
 * @param {(string|URL)} url URL to get file size from
 * @param {number} [timeout=10000] Timeout in milliseconds
 * @param {number} [maxRedirects=5] Maximum number of redirects to follow
 * @return {Promise<number>} File size in bytes
 */
const ufs = (url, timeout = 10000, maxRedirects = 5) => {
    return new Promise((res, rej) => {
        if(url instanceof URL) {
            url = url.toString();
        }
        if(typeof url !== 'string') rej(new TypeError('url must be a string or instance of URL'));
        if(typeof timeout !== 'number') rej(new TypeError('timeout must be a number'));
        if(typeof maxRedirects !== 'number') rej(new TypeError('maxRedirects must be a number'));
        if(maxRedirects < 0) rej(new Error('maxRedirects must be greater than 0'));

        let req = url.startsWith('https://') ? https.get(url, {timeout}) : http.get(url, {timeout});
        req.once("response", r => {
            req.destroy();
            if (r.statusCode >= 300 && r.statusCode < 400 && r.headers.location) {
                if (maxRedirects === 0) {
                    return rej(new Error('Too many redirects'));
                }
                return res(ufs(r.headers.location, timeout, maxRedirects - 1));
            }
            let c = parseInt(r.headers['content-length']);
            if (!isNaN(c)) res(c);
            else rej("Couldn't get file size");
        });
        req.once("error", e => {
            req.destroy();
            rej(e);
        });
        req.once("timeout", e => {
            req.destroy();
            rej(e);
        });
    });
};
module.exports = ufs;