Use let

static/NamespaceLookupWidget.js

@@ -15,7 +15,7 @@
 OO.inheritClass(NamespaceLookupWidget, OO.ui.MenuTagMultiselectWidget);
 
 NamespaceLookupWidget.prototype.clearMenu = function() {
-	var oldValues = this.getValue();
+	let oldValues = this.getValue();
 
 	this.clearItems();
 	this.getMenu().clearItems();
@@ -38,16 +38,16 @@ NamespaceLookupWidget.prototype.setDomain = function(domain) {
 		origin: '*',
 		formatversion: 2
 	}).then(function(res) {
-		var oldValues = this.getValue(),
+		let oldValues = this.getValue(),
 			options = [];
 
 		this.clearItems();
 		this.getMenu().clearItems();
 
-		for (var id in res.query.namespaces) {
+		for (let id in res.query.namespaces) {
 			if (id < 0) continue; // Ignore virtual namespaces
 
-			var info = res.query.namespaces[id];
+			let info = res.query.namespaces[id];
 
 			options.push({
 				data: info.id.toString(),

static/index.js

@@ -1,4 +1,4 @@
-var projectLookup = OO.ui.infuse($('#project')),
+let projectLookup = OO.ui.infuse($('#project')),
 	pageLookup = OO.ui.infuse($('#page'), {
 		domain: projectLookup.getDomain()
 	}),
@@ -13,11 +13,11 @@ var projectLookup = OO.ui.infuse($('#project')),
 		align: 'top'
 	}),
 	out = $('#out'),
-	request = undefined,
+	request,
 	currentSearch = location.search;
 
 function submitForm(pushState) {
-	var params = {
+	let params = {
 			project: projectLookup.getValue(),
 			page: pageLookup.getValue(),
 			namespaces: namespacesSelect.getValue().join(',')
@@ -68,10 +68,10 @@ window.addEventListener('popstate', function() {
 	if (currentSearch === location.search) return;
 	currentSearch = location.search;
 
-	var params = {};
+	let params = {};
 
 	currentSearch.slice(1).split('&').forEach(param => {
-		var chunks = param.split('='),
+		let chunks = param.split('='),
 			key = chunks.shift(),
 			value = decodeURIComponent(chunks.join('='));