Show Passwords with double click

show_password.user.js

// ==UserScript==
// @name         Show Passwords
// @description  Double click on password fields to show password
// @downloadURL  https://gist.github.com/emlyn/979b2820eaa74fea01b8ddc1351a0f60/raw/show_password.user.js
// @updateURL    https://gist.github.com/emlyn/979b2820eaa74fea01b8ddc1351a0f60/raw/show_password.user.js
// @namespace    https://gist.github.com/emlyn
// @version      0.3
// @author       Emlyn Corrin
// @match        http*://*/*
// @grant        none
// ==/UserScript==

(function() {
  'use strict';
  const KEY_ENTER = 13;

  const updateEl = function(el) {
    el.addEventListener('dblclick', () => {
      if (el.type === 'password') {
        el.type = 'text';
      } else {
        el.type = 'password';
      }
    }, false);

    el.addEventListener('blur', () => {
      el.type = 'password';
    }, false);

    el.addEventListener('keydown', e => {
      if (e.keyCode === KEY_ENTER) {
        el.type = 'password';
      }
    }, false);
  };

  const done = new WeakSet();

  const updateAll = function() {
    document.querySelectorAll('input[type=password]').forEach(el => {
      if (!done.has(el)) {
        updateEl(el);
        done.add(el);
      }
    });
  };

  updateAll();

  const observer = new MutationObserver(updateAll);

  observer.observe(document.documentElement, {
    childList: true,
    subtree: true,
    // In case element added as text then changed to password:
    attributes: true,
    attributeFilter: ['type']
  });
})();