luci-theme-bootstrap: use ES6 syntax

Replaced L.bind with arrow functions, used Array.from for array conversion,
applied concise method syntax, and switched to block-scoped declarations.

Signed-off-by: Eamon Xiong <eamonxiong@gmail.com>

themes/luci-theme-bootstrap/htdocs/luci-static/resources/menu-bootstrap.js

@@ -4,7 +4,7 @@
 
 return baseclass.extend({
 	__init__() {
-		ui.menu.load().then(L.bind(this.render, this));
+		ui.menu.load().then((tree) => this.render(tree));
 	},
 
 	render(tree) {

themes/luci-theme-bootstrap/htdocs/luci-static/resources/view/bootstrap/sysauth.js

@@ -3,26 +3,30 @@
 'require view';
 
 return view.extend({
-	render: function() {
-		var form = document.querySelector('form'),
-		    btn = document.querySelector('button');
+	render() {
+		const form = document.querySelector('form');
+		const btn = document.querySelector('button');
 
-		var dlg = ui.showModal(
+		const dlg = ui.showModal(
 			_('Authorization Required'),
-			[].slice.call(document.querySelectorAll('section > *')),
+			Array.from(document.querySelectorAll('section > *')),
 			'login'
 		);
 
-		form.addEventListener('keypress', function(ev) {
-			if (ev.key == 'Enter')
+		form.addEventListener('keypress', (ev) => {
+			if (ev.key === 'Enter')
 				btn.click();
 		});
 
-		btn.addEventListener('click', function() {
-			dlg.querySelectorAll('*').forEach(function(node) { node.style.display = 'none' });
-			dlg.appendChild(E('div', { 'class': 'spinning' }, _('Logging in…')));
+		btn.addEventListener('click', () => {
+			dlg.querySelectorAll('*').forEach((node) => {
+				node.style.display = 'none';
+			});
+			dlg.appendChild(E('div', {
+				class: 'spinning'
+			}, _('Logging in…')));
 
-			form.submit()
+			form.submit();
 		});
 
 		document.querySelector('input[type="password"]').focus();
@@ -30,5 +34,6 @@ return view.extend({
 		return '';
 	},
 
-	addFooter: function() {}
-});
+	addFooter() {},
+
+});