dler

dler

Smart and easy-to-use fetch-based downloader for Node.js compatible runtimes.

[!IMPORTANT]
dler is ESM only, and since it uses the built-in fetch, it requires nodejs>=17.5.0.

Features

• Automatically detect the download file name.
• Bing your own fetch.
• Dependency free.
• Supports resuming downloads.

Limitations

• Does not support multi-threaded or segmented downloads; only sequential downloads are supported.
• Proxy support depends on the runtime's implementation of the fetch function. For example, Deno supports automatic proxy, while Node.js and Bun do not.
  However, this can be addressed by customizing the fetch function.

Installation

$ npm install dler

Usage

import { download } from 'dler';

const url = 'https://api.ip.sb/ip';

// simple
download(url, './ipinfo.txt');

// auto detect file name
download(url);
download(url, 'dirname/');

// with options
download(url, {
    filePath: 'dirname/',
    onProgress: (receivedLength, totalLength) => {
        if (totalLength) console.log((100 * (receivedLength / totalLength)).toFixed(2) + '%');
    },
    onReady: (resp, saveAs) => console.log(`Downloading ${resp.url} to ${saveAs}`),
    /* other options in RequestInit */
    headers: {
        Authorization: 'Bearer xxx',
    },
    signal: AbortSignal.timeout(1000),
});

// use promise
download(url [,options]).then(path => console.log(`File saved to ${path}`));

// use async/await
const absolutePath = await download(url [,options]);

/**
 * Interface representing the initialization options for the downloader.
 * Extends the `RequestInit` interface.
 *
 * Boolean options default to `false` if not specified.
 */
interface DlerInit extends RequestInit {
    /**
     * Optional file path where the downloaded file will be saved.
     * If not provided or if provided as a string ending with '/', the file name will be derived from
     * the `Content-Disposition` header or the basename of the final (maybe redirected) requested URL.
     */
    filePath?: string;

    /**
     * Flag to bypass the default check for HTTP status.
     * By default, the response is considered OK if `response.ok` is true.
     * Set this to `true` to disable this check.
     */
    doNotCheckOK?: boolean;

    /**
     * Flag to enable resuming the download if the file already exists.
     * By default, resumption is not attempted.
     * Set this to `true` to enable download resumption.
     * By default, resumption commences at the file size, which may not be desirable.
     * Specify a number to reset the starting range.
     */
    tryResumption?: boolean | number;

    /**
     * Callback function for monitoring download progress.
     * If `Content-Length` is not provided, `totalLength` will be set to `0`.
     *
     * @param receivedLength - The number of bytes received so far.
     * @param totalLength - The total number of bytes to be received.
     */
    onProgress?: (receivedLength?: number, totalLength?: number) => void;

    /**
     * Callback function invoked when the file is ready to be saved to disk.
     * If a string is returned, the file will be saved to the specified path.
     * This path overrides the `filePath` option.
     *
     * @param resp - The response object from the fetch request.
     * @param saveAs - Suggested file path for saving the file.
     * @returns A string representing the file path where the file should be saved, or a void/Promise resolving to such a string or void.
     */
    onReady?: (resp: Response, saveAs: string) => string | void | Promise<string | void>;
}

Use as a CLI tool (will log a progress bar in console).

import { downloadInCLI } from 'dler';
const progressBarWidth = 50; // default value
await downloadInCLI(url, [options[, progressBarWidth]]);

Use as a global command.

$ npm i dler -g
$ dler --help

Bring your own fetch function.

import { downloadFromFetch } from 'dler';

const myFetch: typeof fetch = async (input, init) => {
    const res = await fetch(input, init);
    console.log(res); // do something...
    return res;
};

const path = await downloadFromFetch(myFetch, 'https://example.net/test.html', {
    filePath: './',
});

Use a ProxyAgent to make requests through a proxy server.

import { fetch as undiciFetch, ProxyAgent } from 'undici';

const myFetch = (url, options) => {
  return undiciFetch(url, {
    ...options,
    dispatcher: new ProxyAgent(<your_proxy_url>)
  })
}

downloadFromFetch(myFetch, 'https://example.net/test.html')

Example

See ./test