[ADD] Blank field validation in Login

web/javascript/login.js

+const BLANK_SPACE_REGEX = /^\s*$/;
+
 function isValidated(){
-    username = document.getElementById("userame").value;
-    pass = document.getElementById("password").value;
-    if (username == "" || pass == ""){
+    var validation = true;
+    validation &= validateBlankInput("username");
+    validation &= validateBlankInput("password");
+
+    if (validation != 1) {
+        alert("All fields must be filled.");
+    }
+    return validation == 1;
+}
+
+function validateBlankInput(inputID) {
+    var value = document.getElementById(inputID).value;
+    if (value == "" || BLANK_SPACE_REGEX.test(value)) {
+        showInvalidInput(inputID);
         return false;
+    } else {
+        hideInvalid(inputID);
+        return true;
+    }
+}
+
+function showInvalidInput(inputID) {
+    highlightInvalid(inputID);
+}
+
+function hideInvalid(inputID) {
+    var border = document.getElementById(inputID).style.border;
+    if (border == "2px solid red") {
+        document.getElementById(inputID).style.border = "";
+    }
+}
+
+function highlightInvalid(inputID) {
+    var border = document.getElementById(inputID).style.border;
+    if (border == "") {
+        document.getElementById(inputID).style.border = "2px solid red";
     }
 }
\ No newline at end of file

web/login/view.php

@@ -9,8 +9,8 @@
                     <div class="content">
                         <h1>LOGIN</h1>
                         <form action="../login/login.php" onsubmit="return (isValidated())" method = "POST">
-                            <p>Username <input type="text" name="username" ></p>
-                            <p>Password <input type="password" name="password" ></p>
+                            <p>Username <input id="username" type="text" name="username" ></p>
+                            <p>Password <input id="password" type="password" name="password" ></p>
                             <p id="account_existence"><a href="/registration">Don\'t have an account?</a></p>
                             <input id="submit_button" type="submit" value="LOGIN">
                         </form>