About

Web-autologin-script.user.js automatically fills the username and password fields.
How it works is described in the script itself in the comments.

In my case:
At work, I have a couple of hundred devices that can be managed via the web interface, quite often I have to login to them.
I’m just tired of constantly entering the username and password on each device, so I wrote this script.

Instructions

Installation through https://openuserjs.org/

1. Download and install Tampermonkey for your browser.
2. Open the link and click on the Install button on the site.
3. Open Tampermonkey preferenses and set settings.

Manual installation

1. Download and install Tampermonkey for your browser.
2. Download web-autologin-script.user.js, open and set your settings.
3. Load web-autologin-script.user.js to Tampermonkey.

Settings

My devices work with http, if you need, you can enable https, add to // ==UserScript==

// @match        http://*/*
// @match        https://*/*

    // SETTINGS
    // If true, script will click on a login button.
    // If false, just fills fields.
    const AUTOLOGIN = false;
    // Enable logs?
    const LOGS = false;
    // How long to wait before the script starts. Set milliseconds.
    const WAIT = 2000;
    // A script will run if the IP address of device is in one of this subnets. | Add your own subnets.
    const SUBNETS = ["192.168.192.0/24", "172.16.0.0/8"];
    // The attributes of the tag Input(you can add NAME or ID or VALUE), which is associated with password field.
    const PASSWORDS = ["textpass", "pinkpanther", "Password", "password"];
        // Some devices don't have the login field. For example: DES-1100-16.
        const PASSWDS = ["pass", "passwd"]
    // The attributes of the tag Input(you can add NAME or ID or VALUE), which is associated with login field.
    const LOGINS = ["textuser", "pelican", "Login", "username"];
    // The attributes of the tag Input(you can add NAME or ID or VALUE), which is associated with submit button.
    const SUBMITS = ["Login", "OK", "login_ok"];
    // Authorization data for devices.
    const LOGIN = '';
    const PASSWORD = '';

FAQ

• I want the login button to be pressed automatically too.

  Just change the value of the variable AUTOLOGIN to true.

  const AUTOLOGIN = true;
  

• The script doesn't work with my device.

  Enable logs to console, change to

  const LOGS = true;  
  

  Open the console panel(chrome shortkey: Control+Shift+J),
  and look at the messages, if the script didn't work, probably it will say what the problem is.

  Most likely it didn't find an attribute for a password/username/submit button field.

  Just find attributes for your device with HTML inspector(Control+Shift+I)
  and add them into variables [PASSWORDS/LOGINS/SUBMITS].

    const PASSWORDS = ["textpass", "pinkpanther", "Password", "password"];
      // For devices that don't have username field.
      const PASSWDS = ["pass", "passwd"]
    const LOGINS = ["textuser", "pelican", "Login", "username"];
    const SUBMITS = ["Login", "OK", "login_ok"];
  

P.S.
This is my first experience with javascript, don't hate me if it looks wrong, better tell me what is wrong.