Fix JS show password in install (#2999)

The button for showing the password was not working in the install.
Updated JavaScript file to ES6 at the same time.

p/scripts/install.js

@@ -1,31 +1,31 @@
 // @license magnet:?xt=urn:btih:0b31508aeb0634b347b8270c7bee4d411b5d4109&dn=agpl-3.0.txt AGPL-3.0
 "use strict";
-/* jshint globalstrict: true */
+/* jshint esversion:6, strict:global */
 
 function show_password(ev) {
-	var button = ev.target;
-	var passwordField = document.getElementById(button.getAttribute('data-toggle'));
+	const button = ev.currentTarget;
+	const passwordField = document.getElementById(button.getAttribute('data-toggle'));
 	passwordField.setAttribute('type', 'text');
 	button.className += ' active';
 	return false;
 }
 function hide_password(ev) {
-	var button = ev.target;
-	var passwordField = document.getElementById(button.getAttribute('data-toggle'));
+	const button = ev.currentTarget;
+	const passwordField = document.getElementById(button.getAttribute('data-toggle'));
 	passwordField.setAttribute('type', 'password');
 	button.className = button.className.replace(/(?:^|\s)active(?!\S)/g , '');
 	return false;
 }
-var toggles = document.getElementsByClassName('toggle-password');
-for (var i = 0 ; i < toggles.length ; i++) {
+const toggles = document.getElementsByClassName('toggle-password');
+for (let i = 0 ; i < toggles.length ; i++) {
 	toggles[i].addEventListener('mousedown', show_password);
 	toggles[i].addEventListener('mouseup', hide_password);
 }
 
+const auth_type = document.getElementById('auth_type');
 function auth_type_change() {
-	var auth_type = document.getElementById('auth_type');
 	if (auth_type) {
-		var auth_value = auth_type.value,
+		const auth_value = auth_type.value,
 			password_input = document.getElementById('passwordPlain');
 
 		if (auth_value === 'form') {
@@ -35,14 +35,13 @@ function auth_type_change() {
 		}
 	}
 }
-var auth_type = document.getElementById('auth_type');
 if (auth_type) {
 	auth_type_change();
 	auth_type.addEventListener('change', auth_type_change);
 }
 
 function mySqlShowHide() {
-	var mysql = document.getElementById('mysql');
+	const mysql = document.getElementById('mysql');
 	if (mysql) {
 		if (document.getElementById('type').value === 'sqlite') {
 			document.getElementById('host').value = '';
@@ -56,20 +55,20 @@ function mySqlShowHide() {
 		}
 	}
 }
-var bd_type = document.getElementById('type');
+const bd_type = document.getElementById('type');
 if (bd_type) {
 	mySqlShowHide();
 	bd_type.addEventListener('change', mySqlShowHide);
 }
 
 function ask_confirmation(ev) {
-	var str_confirmation = ev.target.getAttribute('data-str-confirm');
+	const str_confirmation = ev.target.getAttribute('data-str-confirm');
 	if (!confirm(str_confirmation)) {
 		ev.preventDefault();
 	}
 }
-var confirms = document.getElementsByClassName('confirm');
-for (var i = 0 ; i < confirms.length ; i++) {
+const confirms = document.getElementsByClassName('confirm');
+for (let i = 0 ; i < confirms.length ; i++) {
 	confirms[i].addEventListener('click', ask_confirmation);
 }
 // @license-end