diff --git a/src/_h5ai/public/js/lib/core/event.js b/src/_h5ai/public/js/lib/core/event.js
index 655e385a..16f16e1f 100644
--- a/src/_h5ai/public/js/lib/core/event.js
+++ b/src/_h5ai/public/js/lib/core/event.js
@@ -1,33 +1,27 @@
-const {lo} = require('../globals');
+const isStr = x => typeof x === 'string';
+const isFn = x => typeof x === 'function';
 
 const subscriptions = {};
 
-function sub(topic, listener) {
-    if (lo.isString(topic) && lo.isFunction(listener)) {
+const sub = (topic, listener) => {
+    if (isStr(topic) && isFn(listener)) {
         if (!subscriptions[topic]) {
             subscriptions[topic] = [];
         }
         subscriptions[topic].push(listener);
     }
-}
+};
 
-function unsub(topic, listener) {
-    if (lo.isString(topic) && lo.isFunction(listener) && subscriptions[topic]) {
-        subscriptions[topic] = lo.without(subscriptions[topic], listener);
-    }
-}
-
-function pub(topic, ...args) {
+const pub = (topic, ...args) => {
     // console.log(topic, args);
-    if (lo.isString(topic) && subscriptions[topic]) {
-        lo.each(subscriptions[topic], listener => {
+    if (isStr(topic) && subscriptions[topic]) {
+        subscriptions[topic].forEach(listener => {
             listener.apply(topic, args);
         });
     }
-}
+};
 
 module.exports = {
     sub,
-    unsub,
     pub
 };
diff --git a/src/_h5ai/public/js/lib/server.js b/src/_h5ai/public/js/lib/server.js
index 2ac4e285..29e87eb0 100644
--- a/src/_h5ai/public/js/lib/server.js
+++ b/src/_h5ai/public/js/lib/server.js
@@ -1,6 +1,6 @@
 const {jq, lo} = require('./globals');
 
-function request(data) {
+const request = data => {
     return new Promise(resolve => {
         jq.ajax({
             url: '?',
@@ -11,9 +11,9 @@ function request(data) {
         .done(json => resolve(json))
         .fail(() => resolve());
     });
-}
+};
 
-function formRequest(data) {
+const formRequest = data => {
     const $form = jq('<form method="post" action="?" style="display:none;"/>');
 
     lo.each(data, (val, key) => {
@@ -24,7 +24,7 @@ function formRequest(data) {
     });
 
     $form.appendTo('body').submit().remove();
-}
+};
 
 module.exports = {
     request,
diff --git a/src/_h5ai/public/js/pre.js b/src/_h5ai/public/js/pre.js
index 64970ccd..99a1e1d5 100644
--- a/src/_h5ai/public/js/pre.js
+++ b/src/_h5ai/public/js/pre.js
@@ -1,6 +1,6 @@
 /* eslint-disable func-names,no-var */
 (function (win) {
-    if (typeof win !== 'object' || win.window !== win || !win.document) {
+    if (!win || win.window !== win || !win.document) {
         throw new Error('no-window');
     }
 
@@ -15,26 +15,13 @@
         }
     }
 
-    assert('console', win.console && typeof win.console.log === 'function');
-    assert('assign', win.Object && typeof win.Object.assign === 'function');
-    assert('promise', win.Promise && typeof win.Promise === 'function');
-    assert('history', win.history && typeof win.history.pushState === 'function');
+    function isFn(x) {
+        return typeof x === 'function';
+    }
 
-    assert('canvas', (function () {
-        var elem = win.document.createElement('canvas');
-        return elem.getContext && elem.getContext('2d');
-    }()));
-
-    assert('storage', (function () {
-        var key = '#test#';
-        try {
-            win.localStorage.setItem(key, key);
-            win.localStorage.removeItem(key);
-            return true;
-        } catch (e) {
-            return false;
-        }
-    }()));
+    assert('console', win.console && isFn(win.console.log));
+    assert('assign', win.Object && isFn(win.Object.assign));
+    assert('promise', isFn(win.Promise));
 }(this));
 /* eslint-enable */