diff --git a/components/Fader.jsx b/components/Fader.jsx
index 4857b9c..60fd483 100644
--- a/components/Fader.jsx
+++ b/components/Fader.jsx
@@ -14,7 +14,7 @@ export default class Fader extends React.Component {
   };
 
   onScroll = () => {
-    var scrollableDistance = document.body.scrollHeight - window.innerHeight,
+    const scrollableDistance = document.body.scrollHeight - window.innerHeight,
       scrollTop = window.pageYOffset || document.documentElement.scrollTop,
       distanceToBottom = scrollableDistance - scrollTop;
 
@@ -33,7 +33,7 @@ export default class Fader extends React.Component {
   }
 
   render() {
-    var style = {
+    const style = {
       opacity: this.state.opacity,
     };
 
diff --git a/components/Feed.jsx b/components/Feed.jsx
index dfeb160..1a82133 100644
--- a/components/Feed.jsx
+++ b/components/Feed.jsx
@@ -31,8 +31,8 @@ export default class Feed extends React.Component {
   }
 
   render() {
-    var messages = this.state.messages.map((message, i) => {
-      var image = <img src={message.image} />;
+    const messages = this.state.messages.map((message, i) => {
+      let image = <img src={message.image} />;
 
       if (message.imageLink) {
         image = (
diff --git a/components/InviteForm.jsx b/components/InviteForm.jsx
index b1ea2d6..95617d1 100644
--- a/components/InviteForm.jsx
+++ b/components/InviteForm.jsx
@@ -51,7 +51,7 @@ export default class InviteForm extends React.Component {
   };
 
   render() {
-    var formClasses = classSet({
+    const formClasses = classSet({
       form: true,
       "invite-form": true,
       "has-success": this.state.submitted,
@@ -59,13 +59,13 @@ export default class InviteForm extends React.Component {
       sending: this.state.sending,
     });
 
-    var inputClasses = classSet({
+    const inputClasses = classSet({
       input: true,
       "has-success": this.state.submitted,
       "has-error": this.state.error,
     });
 
-    var feedbackMessage;
+    let feedbackMessage;
 
     if (this.state.error || this.state.submitted) {
       let messageText;
diff --git a/components/Members.jsx b/components/Members.jsx
index c724f3b..061b112 100644
--- a/components/Members.jsx
+++ b/components/Members.jsx
@@ -20,8 +20,8 @@ export default class Members extends React.Component {
   }
 
   render() {
-    var members = this.state.members.map(member => {
-      var src = `${member.avatar_url}&s=120`;
+    const members = this.state.members.map(member => {
+      const src = `${member.avatar_url}&s=120`;
       return <img className="member" key={member.avatar_url} src={src} />;
     });
 
diff --git a/components/api.js b/components/api.js
index ad31be5..1e86105 100644
--- a/components/api.js
+++ b/components/api.js
@@ -1,5 +1,5 @@
-var host = process.env.SERVER || "https://lit-plateau-4689.herokuapp.com/";
+const host = process.env.SERVER || "https://lit-plateau-4689.herokuapp.com/";
 
-export default function(path) {
+export default function getApiURL(path) {
   return host + path;
 }
diff --git a/components/feed-transformers.js b/components/feed-transformers.js
index f8a6047..2a035cb 100644
--- a/components/feed-transformers.js
+++ b/components/feed-transformers.js
@@ -10,15 +10,15 @@ export default {
     return items.filter(isVisibleGithubEvent).map(item => {
       _.templateSettings.interpolate = /{{([\s\S]+?)}}/g;
 
-      var template = _.template(githubEvent.parse(item).text);
+      const template = _.template(githubEvent.parse(item).text);
 
-      var repository = `https://github.com/${item.repo.name}`;
-      var branch;
+      const repository = `https://github.com/${item.repo.name}`;
+      let branch;
       if (item.payload.ref) {
         branch = item.payload.ref.replace("refs/heads/", "");
       }
 
-      var message = template({
+      const message = template({
         repository: `<a target="_blank" href="${repository}">${item.repo.name}</a>`,
         branch: branch,
         number: item.payload.number,
@@ -26,7 +26,7 @@ export default {
         ref: item.payload.ref,
       });
 
-      var url = `https://github.com/${item.actor.login}`;
+      const url = `https://github.com/${item.actor.login}`;
 
       return {
         user: item.actor.login,
@@ -46,7 +46,7 @@ export default {
         item = item.retweeted_status;
       }
 
-      var url = `https://twitter.com/${item.user.screen_name}`;
+      const url = `https://twitter.com/${item.user.screen_name}`;
 
       return {
         user: `@${item.user.screen_name}`,
diff --git a/components/membership/MembershipInfoForm.jsx b/components/membership/MembershipInfoForm.jsx
index 770d88b..a18ee53 100644
--- a/components/membership/MembershipInfoForm.jsx
+++ b/components/membership/MembershipInfoForm.jsx
@@ -5,7 +5,7 @@ import classSet from "classnames";
 import api from "../api";
 import Loader from "../Loader";
 
-var fieldNameTranslations = {
+const fieldNameTranslations = {
   address: { fi: "Osoite" },
   city: { fi: "Paikkakunta" },
   email: { fi: "Sähköpostiosoite" },
@@ -58,7 +58,7 @@ export default class MembershipInfoForm extends React.Component {
   };
 
   onChange = e => {
-    var name = e.target.name;
+    const name = e.target.name;
     if (e.target.value === this.state[name]) {
       return;
     }
@@ -73,7 +73,7 @@ export default class MembershipInfoForm extends React.Component {
   };
 
   getDataErrors = () => {
-    var foundErrors = [];
+    const foundErrors = [];
 
     fieldNames.forEach(fieldName => {
       if (!this.state[fieldName]) {
@@ -91,7 +91,7 @@ export default class MembershipInfoForm extends React.Component {
   render() {
     const inputErrors = this.getDataErrors();
 
-    var formClasses = classSet({
+    const formClasses = classSet({
       form: true,
       "membership-form": true,
       "has-error": inputErrors.length !== 0 || this.state.error,
@@ -99,7 +99,7 @@ export default class MembershipInfoForm extends React.Component {
     });
 
     function getErrorMessage(err) {
-      var feedbackText;
+      let feedbackText;
 
       if (err.type === "missing") {
         feedbackText = `${fieldNameTranslations[err.field].fi} on pakollinen.`;
@@ -115,14 +115,14 @@ export default class MembershipInfoForm extends React.Component {
     }
 
     /* generate error messages */
-    var visibleErrors = inputErrors.filter(
+    const visibleErrors = inputErrors.filter(
       error => this.state.pristineFields.indexOf(error.field) === -1
     );
 
-    var fieldsWithErrors = visibleErrors.map(({ field }) => field);
+    const fieldsWithErrors = visibleErrors.map(({ field }) => field);
 
-    var inputFields = fieldNames.map(fieldName => {
-      var inputClasses = classSet({
+    const inputFields = fieldNames.map(fieldName => {
+      const inputClasses = classSet({
         input: true,
         "has-error": _.includes(fieldsWithErrors, fieldName),
         half: fieldName === "city" || fieldName === "postcode",