diff --git a/.eslintrc b/.eslintrc
new file mode 100644
index 0000000..6a94633
--- /dev/null
+++ b/.eslintrc
@@ -0,0 +1,13 @@
+{
+  "globals": {
+    "console": true,
+    "module": true,
+    "require": true
+  },
+  "env": {
+    "browser": true
+  },
+  "rules": {
+    "quotes": "single"
+  }
+}
diff --git a/Gruntfile.js b/Gruntfile.js
index edb6844..2aa2e74 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -48,6 +48,10 @@ module.exports = function(grunt) {
       }
     },
 
+    eslint: {
+      target: ['lib/**/*.js']
+    },
+
     karma: {
       options: {
         configFile: 'karma.conf.js'
@@ -78,7 +82,7 @@ module.exports = function(grunt) {
     }
   });
 
-  grunt.registerTask('test', 'Run the jasmine and nodeunit tests', ['webpack:global', 'nodeunit', 'karma:single', 'ts']);
+  grunt.registerTask('test', 'Run the jasmine and nodeunit tests', ['eslint', 'webpack:global', 'nodeunit', 'karma:single', 'ts']);
   grunt.registerTask('build', 'Run webpack and bundle the source', ['webpack']);
   grunt.registerTask('publish', 'Prepare the code for release', ['clean', 'test', 'build', 'usebanner', 'update_json']);
 };
diff --git a/lib/adapters/http.js b/lib/adapters/http.js
index 1fb5b2b..0f6266d 100644
--- a/lib/adapters/http.js
+++ b/lib/adapters/http.js
@@ -9,6 +9,8 @@ var pkg = require('./../../package.json');
 var Buffer = require('buffer').Buffer;
 
 module.exports = function httpAdapter(resolve, reject, config) {
+  'use strict';
+
   // Transform request data
   var data = transformData(
     config.data,
@@ -71,9 +73,9 @@ module.exports = function httpAdapter(resolve, reject, config) {
       };
 
       // Resolve or reject the Promise based on the status
-      (res.statusCode >= 200 && res.statusCode < 300
-        ? resolve
-        : reject)(response);
+      (res.statusCode >= 200 && res.statusCode < 300 ?
+        resolve :
+        reject)(response);
     });
   });
 
diff --git a/lib/adapters/xhr.js b/lib/adapters/xhr.js
index 2e4106f..5ae63ce 100644
--- a/lib/adapters/xhr.js
+++ b/lib/adapters/xhr.js
@@ -1,3 +1,5 @@
+/*global ActiveXObject:true*/
+
 var defaults = require('./../defaults');
 var utils = require('./../utils');
 var buildUrl = require('./../helpers/buildUrl');
@@ -7,6 +9,8 @@ var transformData = require('./../helpers/transformData');
 var urlIsSameOrigin = require('./../helpers/urlIsSameOrigin');
 
 module.exports = function xhrAdapter(resolve, reject, config) {
+  'use strict';
+
   // Transform request data
   var data = transformData(
     config.data,
@@ -15,42 +19,42 @@ module.exports = function xhrAdapter(resolve, reject, config) {
   );
 
   // Merge headers
-  var headers = utils.merge(
+  var requestHeaders = utils.merge(
     defaults.headers.common,
     defaults.headers[config.method] || {},
     config.headers || {}
   );
 
   if (utils.isFormData(data)) {
-    delete headers['Content-Type']; // Let the browser set it
+    delete requestHeaders['Content-Type']; // Let the browser set it
   }
 
   // Create the request
-  var request = new(XMLHttpRequest || ActiveXObject)('Microsoft.XMLHTTP');
+  var request = new (XMLHttpRequest || ActiveXObject)('Microsoft.XMLHTTP');
   request.open(config.method.toUpperCase(), buildUrl(config.url, config.params), true);
 
   // Listen for ready state
   request.onreadystatechange = function () {
     if (request && request.readyState === 4) {
       // Prepare the response
-      var headers = parseHeaders(request.getAllResponseHeaders());
+      var responseHeaders = parseHeaders(request.getAllResponseHeaders());
       var responseData = ['text', ''].indexOf(config.responseType || '') !== -1 ? request.responseText : request.response;
       var response = {
         data: transformData(
           responseData,
-          headers,
+          responseHeaders,
           config.transformResponse
         ),
         status: request.status,
         statusText: request.statusText,
-        headers: headers,
+        headers: responseHeaders,
         config: config
       };
 
       // Resolve or reject the Promise based on the status
-      (request.status >= 200 && request.status < 300
-        ? resolve
-        : reject)(response);
+      (request.status >= 200 && request.status < 300 ?
+        resolve :
+        reject)(response);
 
       // Clean up request
       request = null;
@@ -58,18 +62,18 @@ module.exports = function xhrAdapter(resolve, reject, config) {
   };
 
   // Add xsrf header
-  var xsrfValue = urlIsSameOrigin(config.url)
-    ? cookies.read(config.xsrfCookieName || defaults.xsrfCookieName)
-    : undefined;
+  var xsrfValue = urlIsSameOrigin(config.url) ?
+      cookies.read(config.xsrfCookieName || defaults.xsrfCookieName) :
+      undefined;
   if (xsrfValue) {
-    headers[config.xsrfHeaderName || defaults.xsrfHeaderName] = xsrfValue;
+    requestHeaders[config.xsrfHeaderName || defaults.xsrfHeaderName] = xsrfValue;
   }
 
   // Add headers to the request
-  utils.forEach(headers, function (val, key) {
+  utils.forEach(requestHeaders, function (val, key) {
     // Remove Content-Type if data is undefined
     if (!data && key.toLowerCase() === 'content-type') {
-      delete headers[key];
+      delete requestHeaders[key];
     }
     // Otherwise add header to the request
     else {
diff --git a/lib/axios.js b/lib/axios.js
index 4e2847a..ca70bc9 100644
--- a/lib/axios.js
+++ b/lib/axios.js
@@ -6,6 +6,8 @@ var InterceptorManager = require('./core/InterceptorManager');
 
 // Polyfill ES6 Promise if needed
 (function () {
+  'use strict';
+
   // webpack is being used to set es6-promise to the native Promise
   // for the standalone build. It's necessary to make sure polyfill exists.
   var P = require('es6-promise');
@@ -15,6 +17,8 @@ var InterceptorManager = require('./core/InterceptorManager');
 })();
 
 var axios = module.exports = function axios(config) {
+  'use strict';
+
   config = utils.merge({
     method: 'get',
     headers: {},
@@ -69,6 +73,7 @@ axios.defaults = defaults;
 
 // Expose all/spread
 axios.all = function (promises) {
+  'use strict';
   return Promise.all(promises);
 };
 axios.spread = require('./helpers/spread');
@@ -80,29 +85,32 @@ axios.interceptors = {
 };
 
 // Provide aliases for supported request methods
-createShortMethods('delete', 'get', 'head');
-createShortMethodsWithData('post', 'put', 'patch');
+(function () {
+  'use strict';
 
-function createShortMethods() {
-  utils.forEach(arguments, function (method) {
-    axios[method] = function (url, config) {
-      return axios(utils.merge(config || {}, {
-        method: method,
-        url: url
-      }));
-    };
-  });
-}
+  function createShortMethods() {
+    utils.forEach(arguments, function (method) {
+      axios[method] = function (url, config) {
+        return axios(utils.merge(config || {}, {
+          method: method,
+          url: url
+        }));
+      };
+    });
+  }
 
-function createShortMethodsWithData() {
-  utils.forEach(arguments, function (method) {
-    axios[method] = function (url, data, config) {
-      return axios(utils.merge(config || {}, {
-        method: method,
-        url: url,
-        data: data
-      }));
-    };
-  });
-}
+  function createShortMethodsWithData() {
+    utils.forEach(arguments, function (method) {
+      axios[method] = function (url, data, config) {
+        return axios(utils.merge(config || {}, {
+          method: method,
+          url: url,
+          data: data
+        }));
+      };
+    });
+  }
 
+  createShortMethods('delete', 'get', 'head');
+  createShortMethodsWithData('post', 'put', 'patch');
+})();
diff --git a/lib/core/InterceptorManager.js b/lib/core/InterceptorManager.js
index bfac9bb..e3f0cc6 100644
--- a/lib/core/InterceptorManager.js
+++ b/lib/core/InterceptorManager.js
@@ -1,10 +1,9 @@
-'use strict';
-
 var utils = require('./../utils');
 
 function InterceptorManager() {
+  'use strict';
   this.handlers = [];
-};
+}
 
 /**
  * Add a new interceptor to the stack
@@ -15,6 +14,7 @@ function InterceptorManager() {
  * @return {Number} An ID used to remove interceptor later
  */
 InterceptorManager.prototype.use = function (fulfilled, rejected) {
+  'use strict';
   this.handlers.push({
     fulfilled: fulfilled,
     rejected: rejected
@@ -28,6 +28,7 @@ InterceptorManager.prototype.use = function (fulfilled, rejected) {
  * @param {Number} id The ID that was returned by `use`
  */
 InterceptorManager.prototype.eject = function (id) {
+  'use strict';
   if (this.handlers[id]) {
     this.handlers[id] = null;
   }
@@ -42,12 +43,12 @@ InterceptorManager.prototype.eject = function (id) {
  * @param {Function} fn The function to call for each interceptor
  */
 InterceptorManager.prototype.forEach = function (fn) {
+  'use strict';
   utils.forEach(this.handlers, function (h) {
     if (h !== null) {
       fn(h);
-    } 
+    }
   });
 };
 
 module.exports = InterceptorManager;
-
diff --git a/lib/core/dispatchRequest.js b/lib/core/dispatchRequest.js
index f063497..b33f1ae 100644
--- a/lib/core/dispatchRequest.js
+++ b/lib/core/dispatchRequest.js
@@ -1,5 +1,3 @@
-'use strict';
-
 /**
  * Dispatch a request to the server using whichever adapter
  * is supported by the current environment.
@@ -8,6 +6,8 @@
  * @returns {Promise} The Promise to be fulfilled
  */
 module.exports = function dispatchRequest(config) {
+  'use strict';
+
   return new Promise(function (resolve, reject) {
     try {
       // For browsers use XHR adapter
diff --git a/lib/defaults.js b/lib/defaults.js
index 88c6b7b..93fe132 100644
--- a/lib/defaults.js
+++ b/lib/defaults.js
@@ -1,5 +1,3 @@
-'use strict';
-
 var utils = require('./utils');
 
 var JSON_START = /^\s*(\[|\{[^\{])/;
@@ -11,6 +9,7 @@ var DEFAULT_CONTENT_TYPE = {
 
 module.exports = {
   transformRequest: [function (data, headers) {
+    'use strict';
     if (utils.isArrayBuffer(data)) {
       return data;
     }
@@ -28,6 +27,7 @@ module.exports = {
   }],
 
   transformResponse: [function (data) {
+    'use strict';
     if (typeof data === 'string') {
       data = data.replace(PROTECTION_PREFIX, '');
       if (JSON_START.test(data) && JSON_END.test(data)) {
@@ -48,4 +48,4 @@ module.exports = {
 
   xsrfCookieName: 'XSRF-TOKEN',
   xsrfHeaderName: 'X-XSRF-TOKEN'
-};
\ No newline at end of file
+};
diff --git a/lib/helpers/buildUrl.js b/lib/helpers/buildUrl.js
index f624cbe..afcfd4a 100644
--- a/lib/helpers/buildUrl.js
+++ b/lib/helpers/buildUrl.js
@@ -1,8 +1,7 @@
-'use strict';
-
 var utils = require('./../utils');
 
 function encode(val) {
+  'use strict';
   return encodeURIComponent(val).
     replace(/%40/gi, '@').
     replace(/%3A/gi, ':').
@@ -19,6 +18,7 @@ function encode(val) {
  * @returns {string} The formatted url
  */
 module.exports = function buildUrl(url, params) {
+  'use strict';
   if (!params) {
     return url;
   }
diff --git a/lib/helpers/cookies.js b/lib/helpers/cookies.js
index 3c52ef3..42e2138 100644
--- a/lib/helpers/cookies.js
+++ b/lib/helpers/cookies.js
@@ -1,9 +1,8 @@
-'use strict';
-
 var utils = require('./../utils');
 
 module.exports = {
   write: function write(name, value, expires, path, domain, secure) {
+    'use strict';
     var cookie = [];
     cookie.push(name + '=' + encodeURIComponent(value));
 
@@ -27,11 +26,13 @@ module.exports = {
   },
 
   read: function read(name) {
+    'use strict';
     var match = document.cookie.match(new RegExp('(^|;\\s*)(' + name + ')=([^;]*)'));
     return (match ? decodeURIComponent(match[3]) : null);
   },
 
   remove: function remove(name) {
+    'use strict';
     this.write(name, '', Date.now() - 86400000);
   }
-};
\ No newline at end of file
+};
diff --git a/lib/helpers/deprecatedMethod.js b/lib/helpers/deprecatedMethod.js
index dcf93af..f357c7b 100644
--- a/lib/helpers/deprecatedMethod.js
+++ b/lib/helpers/deprecatedMethod.js
@@ -1,5 +1,3 @@
-'use strict';
-
 /**
  * Supply a warning to the developer that a method they are using
  * has been deprecated.
@@ -9,6 +7,9 @@
  * @param {string} [docs] The documentation URL to get further details
  */
 module.exports = function deprecatedMethod(method, instead, docs) {
+  /*eslint-env node*/
+  'use strict';
+
   try {
     console.warn(
       'DEPRECATED method `' + method + '`.' +
diff --git a/lib/helpers/parseHeaders.js b/lib/helpers/parseHeaders.js
index e103634..f7510e0 100644
--- a/lib/helpers/parseHeaders.js
+++ b/lib/helpers/parseHeaders.js
@@ -1,5 +1,3 @@
-'use strict';
-
 var utils = require('./../utils');
 
 /**
@@ -16,9 +14,10 @@ var utils = require('./../utils');
  * @returns {Object} Headers parsed into an object
  */
 module.exports = function parseHeaders(headers) {
+  'use strict';
   var parsed = {}, key, val, i;
 
-  if (!headers) return parsed;
+  if (!headers) { return parsed; }
 
   utils.forEach(headers.split('\n'), function(line) {
     i = line.indexOf(':');
@@ -31,4 +30,4 @@ module.exports = function parseHeaders(headers) {
   });
 
   return parsed;
-};
\ No newline at end of file
+};
diff --git a/lib/helpers/spread.js b/lib/helpers/spread.js
index a7d6ddc..7894ebb 100644
--- a/lib/helpers/spread.js
+++ b/lib/helpers/spread.js
@@ -19,7 +19,8 @@
  * @returns {Function}
  */
 module.exports = function spread(callback) {
+  'use strict';
   return function (arr) {
     callback.apply(null, arr);
   };
-};
\ No newline at end of file
+};
diff --git a/lib/helpers/transformData.js b/lib/helpers/transformData.js
index c764a87..4a25bbd 100644
--- a/lib/helpers/transformData.js
+++ b/lib/helpers/transformData.js
@@ -1,5 +1,3 @@
-'use strict';
-
 var utils = require('./../utils');
 
 /**
@@ -11,9 +9,10 @@ var utils = require('./../utils');
  * @returns {*} The resulting transformed data
  */
 module.exports = function transformData(data, headers, fns) {
+  'use strict';
   utils.forEach(fns, function (fn) {
     data = fn(data, headers);
   });
 
   return data;
-};
\ No newline at end of file
+};
diff --git a/lib/helpers/urlIsSameOrigin.js b/lib/helpers/urlIsSameOrigin.js
index 22b573d..ab58f22 100644
--- a/lib/helpers/urlIsSameOrigin.js
+++ b/lib/helpers/urlIsSameOrigin.js
@@ -1,9 +1,7 @@
-'use strict';
-
-var msie = /(msie|trident)/i.test(navigator.userAgent);
 var utils = require('./../utils');
+var msie = /(msie|trident)/i.test(navigator.userAgent);
 var urlParsingNode = document.createElement('a');
-var originUrl = urlResolve(window.location.href);
+var originUrl;
 
 /**
  * Parse a URL to discover it's components
@@ -12,6 +10,7 @@ var originUrl = urlResolve(window.location.href);
  * @returns {Object}
  */
 function urlResolve(url) {
+  'use strict';
   var href = url;
 
   if (msie) {
@@ -31,12 +30,14 @@ function urlResolve(url) {
     hash: urlParsingNode.hash ? urlParsingNode.hash.replace(/^#/, '') : '',
     hostname: urlParsingNode.hostname,
     port: urlParsingNode.port,
-    pathname: (urlParsingNode.pathname.charAt(0) === '/')
-      ? urlParsingNode.pathname
-      : '/' + urlParsingNode.pathname
+    pathname: (urlParsingNode.pathname.charAt(0) === '/') ?
+              urlParsingNode.pathname :
+              '/' + urlParsingNode.pathname
   };
 }
 
+originUrl = urlResolve(window.location.href);
+
 /**
  * Determine if a URL shares the same origin as the current location
  *
@@ -44,7 +45,8 @@ function urlResolve(url) {
  * @returns {boolean} True if URL shares the same origin, otherwise false
  */
 module.exports = function urlIsSameOrigin(requestUrl) {
+  'use strict';
   var parsed = (utils.isString(requestUrl)) ? urlResolve(requestUrl) : requestUrl;
   return (parsed.protocol === originUrl.protocol &&
         parsed.host === originUrl.host);
-};
\ No newline at end of file
+};
diff --git a/lib/utils.js b/lib/utils.js
index 9f1b32e..ea91be3 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -1,3 +1,4 @@
+/*global toString:true*/
 // utils is a library of generic helper functions non-specific to axios
 
 var toString = Object.prototype.toString;
@@ -9,6 +10,7 @@ var toString = Object.prototype.toString;
  * @returns {boolean} True if value is an Array, otherwise false
  */
 function isArray(val) {
+  'use strict';
   return toString.call(val) === '[object Array]';
 }
 
@@ -19,6 +21,7 @@ function isArray(val) {
  * @returns {boolean} True if value is an ArrayBuffer, otherwise false
  */
 function isArrayBuffer(val) {
+  'use strict';
   return toString.call(val) === '[object ArrayBuffer]';
 }
 
@@ -29,6 +32,7 @@ function isArrayBuffer(val) {
  * @returns {boolean} True if value is an FormData, otherwise false
  */
 function isFormData(val) {
+  'use strict';
   return toString.call(val) === '[object FormData]';
 }
 
@@ -39,6 +43,7 @@ function isFormData(val) {
  * @returns {boolean} True if value is a view on an ArrayBuffer, otherwise false
  */
 function isArrayBufferView(val) {
+  'use strict';
   if ((typeof ArrayBuffer !== 'undefined') && (ArrayBuffer.isView)) {
     return ArrayBuffer.isView(val);
   } else {
@@ -53,6 +58,7 @@ function isArrayBufferView(val) {
  * @returns {boolean} True if value is a String, otherwise false
  */
 function isString(val) {
+  'use strict';
   return typeof val === 'string';
 }
 
@@ -63,6 +69,7 @@ function isString(val) {
  * @returns {boolean} True if value is a Number, otherwise false
  */
 function isNumber(val) {
+  'use strict';
   return typeof val === 'number';
 }
 
@@ -73,6 +80,7 @@ function isNumber(val) {
  * @returns {boolean} True if the value is undefined, otherwise false
  */
 function isUndefined(val) {
+  'use strict';
   return typeof val === 'undefined';
 }
 
@@ -83,6 +91,7 @@ function isUndefined(val) {
  * @returns {boolean} True if value is an Object, otherwise false
  */
 function isObject(val) {
+  'use strict';
   return val !== null && typeof val === 'object';
 }
 
@@ -93,6 +102,7 @@ function isObject(val) {
  * @returns {boolean} True if value is a Date, otherwise false
  */
 function isDate(val) {
+  'use strict';
   return toString.call(val) === '[object Date]';
 }
 
@@ -103,6 +113,7 @@ function isDate(val) {
  * @returns {boolean} True if value is a File, otherwise false
  */
 function isFile(val) {
+  'use strict';
   return toString.call(val) === '[object File]';
 }
 
@@ -113,6 +124,7 @@ function isFile(val) {
  * @returns {boolean} True if value is a Blob, otherwise false
  */
 function isBlob(val) {
+  'use strict';
   return toString.call(val) === '[object Blob]';
 }
 
@@ -123,6 +135,7 @@ function isBlob(val) {
  * @returns {String} The String freed of excess whitespace
  */
 function trim(str) {
+  'use strict';
   return str.replace(/^\s*/, '').replace(/\s*$/, '');
 }
 
@@ -139,6 +152,7 @@ function trim(str) {
  * @param {Function} fn The callback to invoke for each item
  */
 function forEach(obj, fn) {
+  'use strict';
   // Don't bother if no value provided
   if (obj === null || typeof obj === 'undefined') {
     return;
@@ -154,7 +168,7 @@ function forEach(obj, fn) {
 
   // Iterate over array values
   if (isArrayLike) {
-    for (var i=0, l=obj.length; i<l; i++) {
+    for (var i = 0, l = obj.length; i < l; i++) {
       fn.call(null, obj[i], i, obj);
     }
   }
@@ -185,7 +199,8 @@ function forEach(obj, fn) {
  * @param {Object} obj1 Object to merge
  * @returns {Object} Result of all merge properties
  */
-function merge(obj1/*, obj2, obj3, ...*/) {
+function merge(/*obj1, obj2, obj3, ...*/) {
+  'use strict';
   var result = {};
   forEach(arguments, function (obj) {
     forEach(obj, function (val, key) {
diff --git a/package.json b/package.json
index 56447ce..88d657e 100644
--- a/package.json
+++ b/package.json
@@ -33,6 +33,7 @@
     "grunt-contrib-clean": "^0.6.0",
     "grunt-contrib-nodeunit": "^0.4.1",
     "grunt-contrib-watch": "^0.6.1",
+    "grunt-eslint": "^9.0.0",
     "grunt-karma": "^0.10.1",
     "grunt-ts": "^3.0.0",
     "grunt-update-json": "^0.2.1",