Derver

Tiny Development Server for your web-applications with livereload and watchers

Features

• Very tiny (~8kb)
• Livereload
• Watch directories with callback
• CLI or JS API
• Supports Gzip or Brotli compression
• Cache control
• Supports SPA mode

CLI Usage

derver [parameters] [serve_directory]

You may use npx derver instantly or install globally by npm install -g derver and then use command derver.

To serve and watching current directory just run:

derver

Server will run on http://localhost:7000 and site will be reloaded each time you change the file in the served directory.

By default server is running on localhost and nobody can access on the website from the network. Bind server on the 0.0.0.0 interface to allow network connections:

derver --host=0.0.0.0 public

In this example, public is a directory where are files for serving. By default it is current directory.

List of possible parameters

--host

Interface, where bind the server. Use 0.0.0.0 inside Docker container or when need network connections to your site. Default: localhost Example: --host=localhost

--port

Port, where bind the server. Default: 7000 Example: --port=8080

--index

Name of the root file of web directory. Webserver will lookup this file when no file specified in the requested URL. Default: index.html Example: --index=index.htm

--watch

Specify the directories for watching files changes. Each time when files modified in these directories, website will be reloaded. You may use this parameter multiple times to set more than one directory for watching. Default: watch the served directory Example: --watch=dist/public --watch=src

--no-watch

Add this parameter when you want to disable any watching and livereloading. Example: --no-watch

--compress

Will return files compressed by gzip or brotli, if client supports it. Example: --compress

--cache

Add Cache-control header to the response with max-age equal 31536000 (~1 year). You can specify number of seconds. Example: --cache Example: --cache=3600

--scroll

Restore scroll position on every reload. Number value is equal timeout before scroll restoration. Example: --scroll Example: --scroll=100

--spa

Enables SPA (Single-Page Application) mode. All requested pages will be responsed by index page in the application root, which is specified in --index parameter. Example: --spa

--production

Run server in production mode(really not, use at own risk). It enables --cache, --compress and --no-watch parameters. Also host will set on 0.0.0.0 to handle connections from the network.

Example: --production

Javascript API

You may use Derver in the your scripts to get more power.

Install Derver as local dependency:

npm install derver

Then use derver function from the derver package to start the server.

import {derver} from 'derver';

derver();

By default, server will be started on http://localhost:7000 and serve public directory in your workdir.

Configuration

You may set configuration object as a parameter of the derver function. Below you find all possible options:

dir string|boolean

Directory which contains files for serving. If nothing set in watch option, it will be watching for changes also. When it is false - no files would be serving, only middlewares will work.

Default: public

Example: dir: 'public' Example: dir: false

host string

Interface, where bind the server. Use 0.0.0.0 inside docker or when need network connections to your site.

Default: localhost

Example: host: 'localhost'

port number

Port, where bind the server.

Default: 7000

Example: port: 8080

index string

Name of the root file of web directory. Webserver will lookup this file when no file specified in the requested URL.

Default: index.html

Example: index: 'index.htm'

compress boolean

Will return files compressed by gzip or brotli, if client supports it.

Default: false

Example: compress: true

cache boolean|number

Add Cache-control header to the response with max-age equal 31536000 (~1 year). You can specify number of seconds.

Default: false

Example: cache: true

Example: cache: 3600

spa boolean

Enables SPA (Single-Page Application) mode. All requested pages will be responced by index page in the application root, which is specified in index option.

Default: false

Example: spa: true

watch string|array of string

Specify the directories for watching filechanges. Each time when files modified in theese directories, website will be reloaded and onwatch callback will be run. By default will be watched directory defined in dir option.

Default: null

Example: watch: ['dist/public','src']

remote boolean|string

Enables remote control listener. See Remote control

Default: false

Example: remote: true

Example: remote: "my_dev_server"

parseJson boolean

When incoming request sent with type application/json Derver will parse its body and put object in request.body.

Default: true

Example: parseJson: true

preserveScroll boolean|number

Restore scroll position on every reload. Number value is equal timeout before scroll restoration.

Default: false

Example: preserveScroll: true

Example: preserveScroll: 100

banner boolean

Show or not the banner in console when server starts.

Default: true

Example: banner: false

log boolean

Show or not file requests in console

Default: true

Example: log: false

onwatch function

This function will be called when any file changes in watched directories.

Default: null

Example: onwatch: (liverload,watchitem)=>{if(watchitem == 'src') livereload.prevent()})

onwatch-callback arguments

Callback signature: (livereload,watchitem,filename,eventname)

livereload

It is object with following methods:

• livereload.prevent() - Will stop sheduled livereload action for this watch event.
• livereload.reload() - Run each time you want to reload page in the browser.
• livereload.console(message) - Send a message to the browser console.
• livereload.error(message,[header]) - Show error modal on client.

watchitem

It is a string with directory name where were fired filechange event. It is same string as you specified in watch option(or in dir option, if watch not set).

filename

Full path of changed file (unstable)

eventname

What exactly happened with modified file.

Using Middlewares

You may use any common middleware(like Express middlewares) to add additional functionality for you server. derver() function returns the object with methods:

• sub - run callback to register middlewares for specified subpath
• use - run middleware for all HTTP methods
• get - run middleware for GET method only
• post - run middleware for POST method only
• ...actually you can write any HTTP method here

derver()
 .use(middleware1)
 .get('/api',middleware2)
 .put('/clear',middleware3,middleware4)

Pattern

If first argument for these methods is a pattern of the URL, middleware will run only if request's URL is matched with its path.

The pattern may looks like /foo of /foo/bar. If no pattern provided, middleware will run on each request.

Pattern also may have a parameters /user/:name and when URL will be /user/bob or /user/alex you can get the value(alex or bob) from request.params.name property.

derver()
.use('/user/:name',middleware)

Writing middleware function

The middleware functions gets three arguments - common Node's request,response objects and next function, which will run next middleware. If your middleware doesn't response on request, you must run next() or request never will be ended.

Lets see an example for client and API middleware:

 function myLogMiddleware(req,resp,next){
   console.log('Current URL is: ' + req.url);
   next();
 }

 function myHelloMiddleware(req,resp){
   resp.send('Hello, '+req.params.name);
 }

 derver()
   .use(myLogMiddleware)
   .get('/hello/:name',myHelloMiddleware)

Additional data from incoming request extension

The request argument is Node's http.IncomingMessage object. But it is expanded with few useful data:

• path - pathname of current URL
• search - query params as a string
• query - query params as an object
• host - host from header(including port)
• hostname - host from header(without port)
• port - port from header

If request sent with type application/json you will get the parsed object from request.body. To avoid this, set parseJson option to false;

Send JSON object in responce

Method responce.send(message) will send content of message with status code 200. If message is a simple object, Derver will automaticly stringify it and send to client with Content-type: application/json header.

Nested middlewares

In case you need to run middlewares which are situated under specified sub path use .sub() method.

derver()
  .sub('/api',(app)=>
    // will run on  every request starting with '/api/...'
    app.use(myLogMiddleware);

    // will run when URL will be '/api/hello/bob'
    app.get('/hello/bob',myHelloMiddleware);

    app.sub('/users',(app)=>{
        // will run when URL will be '/api/users/add'
        app.post('/add',myUserAddMiddleware);
    })
  })

Remote control

There is a way to perform some actions in currently opened browser windows. For example you want to reload page from external script.

import {createRemote} from 'derver';

// Create remote object with parameters of running server
const remote = createRemote({host:'localhost',port:7000}); // there are defaults, may be dropped

// Also you can call `createRemote('my_dev_server)` with server ID specified in remote option.

// Reload page in all opened browser windows
remote.reload();

// Send some text in the browser console
remote.console('Hello!');

// Show modal with error message
remote.error('Error happened! Fix it as soon as possible!','Error header');

Note: don't forget to enable remote option in Derver's configuration

How livereload works

When you changes file in the watching directory, server will send command to the client side to reload current page. It is musthave feature when you developing web-application and want to see changes immediately.

Livereload made with Server Sent Events API. It is perfect feature for one-way communication server with client based only on http protocol. It is why Derver is so tiny, no need to implement websocket communication as others known servers do.

Some JavaScript code for livereload will be added before </body> element inside each requested html file.