diff --git a/.gitignore b/.gitignore
index 39b7a9743..df78af391 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,12 +2,11 @@ node_modules/
 *~
 *.db
 *.DS_Store
-tmp/
-testbuilds/
-test.html
-captchas.html
-install.json
-Gruntfile.js
-.jshintrc
-.tests_enabled
-.events
+/tmp/
+/testbuilds/
+/test.html
+/captchas.html
+/install.json
+/.jshintrc
+/.tests_enabled
+/.events
diff --git a/tools/.jshintrc b/tools/.jshintrc
new file mode 100644
index 000000000..0c9613612
--- /dev/null
+++ b/tools/.jshintrc
@@ -0,0 +1,6 @@
+{
+  "esnext": true,
+  "undef":  true,
+  "unused": true,
+  "node":   true
+}
diff --git a/tools/install.js b/tools/install.js
index 86c20cbfe..92ef8e503 100644
--- a/tools/install.js
+++ b/tools/install.js
@@ -1,8 +1,8 @@
 var fs = require('fs-extra');
 
 var installMap = fs.readJsonSync('install.json');
-for (src in installMap) {
-  for (dest of installMap[src]) {
+for (var src in installMap) {
+  for (var dest of installMap[src]) {
     fs.copySync(src, dest);
   }
 }
diff --git a/tools/sign.js b/tools/sign.js
index 86f88bb03..04b151f85 100644
--- a/tools/sign.js
+++ b/tools/sign.js
@@ -1,14 +1,14 @@
-fs = require('fs');
-crx = require('crx');
+var fs = require('fs');
+var crx = require('crx');
 
 var pkg = JSON.parse(fs.readFileSync('package.json', 'utf8'));
 var channel = process.argv[2] || '';
 
-var privateKey = fs.readFileSync(`../${pkg.meta.path}.keys/${pkg.name}.pem`)
+var privateKey = fs.readFileSync(`../${pkg.meta.path}.keys/${pkg.name}.pem`);
 var archive = fs.readFileSync(`testbuilds/${pkg.name}${channel}.crx.zip`);
 var extension = new crx({privateKey, loaded: true});
 extension.pack(archive).then((data) =>
   fs.writeFileSync(`testbuilds/${pkg.name}${channel}.crx`, data)
-).catch(function(err) {
+).catch(function() {
   process.exit(1);
 });
diff --git a/tools/zip-crx.js b/tools/zip-crx.js
index 519b0046b..e50414c28 100644
--- a/tools/zip-crx.js
+++ b/tools/zip-crx.js
@@ -6,14 +6,14 @@ var v = JSON.parse(fs.readFileSync('version.json', 'utf8'));
 var channel = process.argv[2] || '';
 
 var zip = new JSZip();
-for (file of ['eventPage.js', 'icon128.png', 'icon16.png', 'icon48.png', 'manifest.json', 'script.js']) {
+for (var file of ['eventPage.js', 'icon128.png', 'icon16.png', 'icon48.png', 'manifest.json', 'script.js']) {
   zip.file(
     file,
     fs.readFileSync(`testbuilds/crx${channel}/${file}`),
     {date: new Date(v.date)}
   );
 }
-output = zip.generate({
+var output = zip.generate({
   type: 'nodebuffer',
   compression: 'DEFLATE',
   compressionOptions: {level: 9},