Add new power button feature

api/controller.js

@@ -15,6 +15,7 @@ exports.calculate = function(req, res) {
     'subtract': function(a, b) { return a - b },
     'multiply': function(a, b) { return a * b },
     'divide':   function(a, b) { return a / b },
+    'power':    function(a, b) { return Math.pow(a, b); },
   };
 
   if (!req.query.operation) {

public/client.js

@@ -32,6 +32,9 @@ function calculate(operand1, operand2, operation) {
         case '/':
             uri += "?operation=divide";
             break;
+        case '^':
+            uri += "?operation=power";
+            break;
         default:
             setError();
             return;
@@ -137,7 +140,7 @@ document.addEventListener('keypress', (event) => {
         numberPressed(event.key);
     } else if (event.key == '.') {
         decimalPressed();
-    } else if (event.key.match(/^[-*+/]$/)) {
+    } else if (event.key.match(/^[-*+\/]$/) || event.key == '^') {
         operationPressed(event.key);
     } else if (event.key == '=') {
         equalPressed();

public/default.css

@@ -167,6 +167,11 @@ BODY {
     grid-column: span 2;
 }
 
+/* utility class for buttons that should stretch across all four columns */
+.span-4 {
+    grid-column: span 4;
+}
+
 .calculator-buttons {
     display: grid;
     grid-template-columns: repeat(4, 1fr);

public/index.html

@@ -37,8 +37,12 @@
 
             <button class="btn" onClick="numberPressed(0)">0</button>
             <button class="btn" onClick="decimalPressed()">.</button>
+            <!-- power / exponent button -->
+            <button class="btn" onClick="operationPressed('^')">^</button>
             <button class="btn" onClick="operationPressed('+')">+</button>
-            <button class="btn" onClick="equalPressed()">=</button>
+            <button class="btn span-4" onClick="equalPressed()">=</button>
+
+
 
           </div>
         </div>

test/arithmetic.test.js

@@ -93,8 +93,35 @@ describe('Arithmetic', function () {
         });
     });
 
-// TODO: Challenge #1
-
+
+    // Exponentiation function was added (operation=power)
+    describe('Exponentiation', function () {
+        it('raises a positive integer to a positive integer', function (done) {
+            request.get('/arithmetic?operation=power&operand1=2&operand2=3')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 8 });
+                    done();
+                });
+        });
+        it('power of zero exponent returns 1', function (done) {
+            request.get('/arithmetic?operation=power&operand1=5&operand2=0')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 1 });
+                    done();
+                });
+        });
+        it('power with negative exponent produces fractional result', function (done) {
+            request.get('/arithmetic?operation=power&operand1=2&operand2=-2')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 0.25 });
+                    done();
+                });
+        });
+    });
+
 
     describe('Multiplication', function () {
         it('multiplies two positive integers', function (done) {