MAPG-115 add login functionality

public/static/js/login.js

@@ -0,0 +1,42 @@
+(function () {
+    var form = document.getElementById('loginForm');
+
+    form.onsubmit = function (e) {
+        document.getElementById('loading').style.visibility = 'visible';
+
+        e.preventDefault();
+
+        var formData = new FormData(form);
+
+        var xhr = new XMLHttpRequest();
+        xhr.responseType = 'json';
+        xhr.onload = function () {
+            document.getElementById('loading').style.visibility = 'hidden';
+
+            if (this.response.error) {
+                var errorText;
+                switch (this.response.error) {
+                    case 'user_not_found':
+                        errorText = 'No user found with the given email address.';
+                        break;
+                    case 'password_not_match':
+                        errorText = 'The given password is wrong.'
+                        break;
+                }
+
+                var loginFormError = document.getElementById('loginFormError');
+                loginFormError.style.display = 'block';
+                loginFormError.innerHTML = errorText;
+
+                form.elements.email.select();
+
+                return;
+            }
+
+            window.location.replace('/');
+        };
+
+        xhr.open('POST', form.action, true);
+        xhr.send(formData);
+    };
+})();