diff --git a/annotate-page/sidebar/panel.js b/annotate-page/sidebar/panel.js
index f4fdb46..2af8505 100644
--- a/annotate-page/sidebar/panel.js
+++ b/annotate-page/sidebar/panel.js
@@ -4,14 +4,14 @@ const contentBox = document.querySelector("#content");
 /*
 Make the content box editable as soon as the user mouses over the sidebar.
 */
-window.addEventListener("mouseover", (e) => {
+window.addEventListener("mouseover", () => {
   contentBox.setAttribute("contenteditable", true);
 });
 
 /*
 When the user mouses out, save the current contents of the box.
 */
-window.addEventListener("mouseout", (e) => {
+window.addEventListener("mouseout", () => {
   contentBox.setAttribute("contenteditable", false);
   browser.tabs.query({windowId: myWindowId, active: true}).then((tabs) => {
     let contentToStore = {};
diff --git a/apply-css/background.js b/apply-css/background.js
index 7e936a0..3c0b1aa 100644
--- a/apply-css/background.js
+++ b/apply-css/background.js
@@ -51,7 +51,7 @@ When first loaded, initialize the page action for all tabs.
 */
 var gettingAllTabs = browser.tabs.query({});
 gettingAllTabs.then((tabs) => {
-  for (tab of tabs) {
+  for (let tab of tabs) {
     initializePageAction(tab);
   }
 });
diff --git a/commands/background.js b/commands/background.js
index 825c559..a54dc95 100644
--- a/commands/background.js
+++ b/commands/background.js
@@ -12,7 +12,7 @@
  */
 var gettingAllCommands = browser.commands.getAll();
 gettingAllCommands.then((commands) => {
-  for (command of commands) {
+  for (let command of commands) {
     console.log(command);
   }
 });
diff --git a/emoji-substitution/emojiMap.js b/emoji-substitution/emojiMap.js
index 16c689e..b2f1b9e 100644
--- a/emoji-substitution/emojiMap.js
+++ b/emoji-substitution/emojiMap.js
@@ -2,6 +2,8 @@
  * This file contains the Map of word --> emoji substitutions.
  */
 
+/* exported sortedEmojiMap */
+
 let dictionary = new Map();
 dictionary.set('apple', '🍎');
 dictionary.set('banana', '🍌');
diff --git a/emoji-substitution/substitute.js b/emoji-substitution/substitute.js
index c886063..39203db 100644
--- a/emoji-substitution/substitute.js
+++ b/emoji-substitution/substitute.js
@@ -3,6 +3,8 @@
  * all occurrences of each mapped word with its emoji counterpart.
  */
 
+/*global sortedEmojiMap*/
+
 // emojiMap.js defines the 'sortedEmojiMap' variable.
 // Referenced here to reduce confusion.
 const emojiMap = sortedEmojiMap;
diff --git a/google-userinfo/background/authorize.js b/google-userinfo/background/authorize.js
index 633c41b..b49bb72 100644
--- a/google-userinfo/background/authorize.js
+++ b/google-userinfo/background/authorize.js
@@ -1,3 +1,5 @@
+/* exported getAccessToken */
+
 const REDIRECT_URL = browser.identity.getRedirectURL();
 const CLIENT_ID = "YOUR-CLIENT-ID";
 const SCOPES = ["openid", "email", "profile"];
diff --git a/google-userinfo/background/main.js b/google-userinfo/background/main.js
index ac70222..9ddf1fb 100644
--- a/google-userinfo/background/main.js
+++ b/google-userinfo/background/main.js
@@ -1,3 +1,5 @@
+/*global getAccessToken*/
+
 function notifyUser(user) {
   browser.notifications.create({
     "type": "basic",
diff --git a/google-userinfo/background/userinfo.js b/google-userinfo/background/userinfo.js
index 84a5427..5f7ac1d 100644
--- a/google-userinfo/background/userinfo.js
+++ b/google-userinfo/background/userinfo.js
@@ -2,6 +2,9 @@
 Fetch the user's info, passing in the access token in the Authorization
 HTTP request header.
 */
+
+/* exported getUserInfo */
+
 function getUserInfo(accessToken) {
   const requestURL = "https://www.googleapis.com/oauth2/v1/userinfo?alt=json";
   const requestHeaders = new Headers();
diff --git a/history-deleter/history.js b/history-deleter/history.js
index 11a1dff..798f8db 100644
--- a/history-deleter/history.js
+++ b/history-deleter/history.js
@@ -7,7 +7,7 @@ function get_hostname(url) {
 }
 
 function set_domain(domain) {
-  spans = document.getElementsByClassName('domain');
+  const spans = document.getElementsByClassName('domain');
   [].slice.call(spans).forEach((span) => {
     span.textContent = domain;
   });
@@ -65,7 +65,7 @@ function clearAll(e) {
     // Loop through them and delete them one by one.
     var searchingHistory = browser.history.search({text: hostname})
     searchingHistory.then((results) => {
-        for (k = 0; k < results.length; k++) {
+        for (let k of results) {
           browser.history.deleteUrl({url: results[k].url});
         }
         // Clear out the UI.
diff --git a/list-cookies/cookies.js b/list-cookies/cookies.js
index 74c5a84..db2fc8e 100644
--- a/list-cookies/cookies.js
+++ b/list-cookies/cookies.js
@@ -1,6 +1,6 @@
 function showCookiesForTab(tabs) {
   //get the first tab object in the array
-  tab = tabs.pop();
+  let tab = tabs.pop();
 
   //get all cookies in the domain
   var gettingAllCookies = browser.cookies.getAll({url: tab.url});
@@ -14,22 +14,22 @@ function showCookiesForTab(tabs) {
 
     if (cookies.length > 0) {
       //add an <li> item with the name and value of the cookie to the list
-      for (cookie of cookies) {
-        var li = document.createElement("li");
-        var content = document.createTextNode(cookie.name + ": "+ cookie.value);
+      for (let cookie of cookies) {
+        let li = document.createElement("li");
+        let content = document.createTextNode(cookie.name + ": "+ cookie.value);
         li.appendChild(content);
         cookieList.appendChild(li);
       }
     } else {
-      var p = document.createElement("p");
-      var content = document.createTextNode("No cookies in this tab.");
-      var parent = cookieList.parentNode;
+      let p = document.createElement("p");
+      let content = document.createTextNode("No cookies in this tab.");
+      let parent = cookieList.parentNode;
 
       p.appendChild(content);
       parent.appendChild(p);
     }
   });
-};
+}
 
 //get active tab to run an callback function.
 //it sends to our callback an array of tab objects
diff --git a/proxy-blocker/proxy/proxy-script.js b/proxy-blocker/proxy/proxy-script.js
index 135295c..31343e6 100644
--- a/proxy-blocker/proxy/proxy-script.js
+++ b/proxy-blocker/proxy/proxy-script.js
@@ -1,3 +1,5 @@
+/* exported FindProxyForURL */
+
 var blockedHosts = [];
 const allow = "DIRECT 1234";
 const deny = "PROXY 127.0.0.1:65535";
diff --git a/selection-to-clipboard/content-script.js b/selection-to-clipboard/content-script.js
index 8fb2598..1b78c5b 100644
--- a/selection-to-clipboard/content-script.js
+++ b/selection-to-clipboard/content-script.js
@@ -1,7 +1,7 @@
 /*
 copy the selected text to clipboard
 */
-function copySelection(e) {
+function copySelection() {
     var selectedText = window.getSelection().toString().trim();
 
     if (selectedText) {
diff --git a/tabs-tabs-tabs/tabs.js b/tabs-tabs-tabs/tabs.js
index dba3dfc..c6eb22b 100644
--- a/tabs-tabs-tabs/tabs.js
+++ b/tabs-tabs-tabs/tabs.js
@@ -163,7 +163,7 @@ document.addEventListener("click", function(e) {
   // Currently (11/2/2016) only supported by Chrome
   else if (e.target.id === "tabs-highlight") { // highlights current tab and next tab (cycles back to first tab if current tab is the last one)
     callOnActiveTab((tab, tabs) => {
-      next = (tab.index+1) % tabs.length;
+      let next = (tab.index+1) % tabs.length;
       browser.tabs.highlight({tabs:[tab.index, next]});
     });
   }
diff --git a/window-manipulator/window.js b/window-manipulator/window.js
index d6e36eb..a659b48 100644
--- a/window-manipulator/window.js
+++ b/window-manipulator/window.js
@@ -26,48 +26,48 @@ document.addEventListener("click", (e) => {
   }
 
   else if (e.target.id === "window-create-normal") {
-    var createData = {};
-    var creating = browser.windows.create(createData);
+    let createData = {};
+    let creating = browser.windows.create(createData);
     creating.then(() => {
       console.log("The normal window has been created");
     });
   }
 
   else if (e.target.id === "window-create-incognito") {
-    var createData = {
+    let createData = {
       incognito: true,
     };
-    var creating = browser.windows.create(createData);
+    let creating = browser.windows.create(createData);
     creating.then(() => {
       console.log("The incognito window has been created");
     });
   }
 
   else if (e.target.id === "window-create-panel") {
-    var createData = {
+    let createData = {
       type: "panel",
     };
-    var creating = browser.windows.create(createData);
+    let creating = browser.windows.create(createData);
     creating.then(() => {
       console.log("The panel has been created");
     });
   }
 
   else if (e.target.id === "window-create-detached-panel") {
-    var createData = {
+    let createData = {
       type: "detached_panel",
     };
-    var creating = browser.windows.create(createData);
+    let creating = browser.windows.create(createData);
     creating.then(() => {
       console.log("The detached panel has been created");
     });
   }
 
   else if (e.target.id === "window-create-popup") {
-    var createData = {
+    let createData = {
       type: "popup",
     };
-    var creating = browser.windows.create(createData);
+    let creating = browser.windows.create(createData);
     creating.then(() => {
       console.log("The popup has been created");
     });