power function added

Author: stargazer4

api/controller.js

@@ -16,6 +16,7 @@ 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 },
+    'pow':      function(a, b) { return Math.pow(a, b) }
   };
 
   if (!req.query.operation) {

public/client.js

@@ -33,6 +33,9 @@ function calculate(operand1, operand2, operation) {
         case '/':
             uri += "?operation=divide";
             break;
+        case '^':
+            uri += "?operation=pow";
+            break;
         default:
             setError();
             return;

public/index.html

@@ -41,6 +41,8 @@
             <button class="btn" onClick="equalPressed()">=</button>
 
             <!-- TODO: Buttons -->
+            <!-- add a button for a power (or exponential) function -->
+            <button class="btn" onClick="operationPressed('^')">^</button>
           </div>
         </div>
       </div>

test/arithmetic.test.js

@@ -94,6 +94,58 @@ describe('Arithmetic', function () {
     });
 
 // TODO: Challenge #1
+
+    // add tests for subtraction, multiplication, division, and exponentiation
+    describe('Subtraction', function () {
+        it('subtracts two positive integers', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=21&operand2=21')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 0 });
+                    done();
+                });
+        });
+        it('subtracts zero from an integer', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=42&operand2=0')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 42 });
+                    done();
+                });
+        });
+        it('subtracts a negative integer from a positive integer', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=21&operand2=-42')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 63 });
+                    done();
+                });
+        });
+        it('subtracts two negative integers', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=-21&operand2=-21')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 0 });
+                    done();
+                });
+        });
+        it('subtracts an integer from a floating point number', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=2.5&operand2=-5')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 7.5 });
+                    done();
+                });
+        });
+        it('subtracts with negative exponent', function (done) {
+            request.get('/arithmetic?operation=subtract&operand1=1.2e-5&operand2=-1.2e-5')
+                .expect(200)
+                .end(function (err, res) {
+                    expect(res.body).to.eql({ result: 2.4e-5 });
+                    done();
+                });
+        });
+    }
 
 
     describe('Multiplication', function () {