create a calculator that does the following:

add, subtract, get the sum, multiply, get the power, and find the factorial

08_calculator/calculator.js

@@ -1,25 +1,46 @@
-const add = function() {
+const add = function(a, b) {
+	let addition = a + b;
+  return addition;
+};
+
+const subtract = function(a, b) {
+  let sub = a - b;
+  return sub;
 	
 };
 
-const subtract = function() {
-	
+const sum = function(array) {
+  let sum = 0;
+  array.forEach(item => {
+    sum += item;
+  });
+  return sum;
+}
+
+
+const multiply = function(array) {
+  
+  var sum = 1;
+  for (var i = 0; i < array.length; i++) {
+      sum = sum * array[i];
+  } 
+  return sum;
+}
+
+
+
+const power = function(a, b) {
+  let expo = a ** b;
+  return expo;
 };
 
-const sum = function() {
-	
-};
-
-const multiply = function() {
-
-};
-
-const power = function() {
-	
-};
-
-const factorial = function() {
-	
+const factorial = function(input) {
+if (input === 0 || input === 1)
+  return 1;
+for (let i = input - 1; i >= 1; i--) {
+  input *= i;
+}
+return input;
 };
 
 // Do not edit below this line

08_calculator/calculator.spec.js

@@ -5,73 +5,73 @@ describe('add', () => {
 		expect(calculator.add(0,0)).toBe(0);
 	});
 
-	test.skip('adds 2 and 2', () => {
+	test('adds 2 and 2', () => {
 		expect(calculator.add(2,2)).toBe(4);
 	});
 
-	test.skip('adds positive numbers', () => {
+	test('adds positive numbers', () => {
 		expect(calculator.add(2,6)).toBe(8);
 	});
 });
 
 describe('subtract', () => {
-	test.skip('subtracts numbers', () => {
+	test('subtracts numbers', () => {
 		expect(calculator.subtract(10,4)).toBe(6);
 	});
 });
 
 describe('sum', () => {
-	test.skip('computes the sum of an empty array', () => {
+	test('computes the sum of an empty array', () => {
 		expect(calculator.sum([])).toBe(0);
 	});
 
-	test.skip('computes the sum of an array of one number', () => {
+	test('computes the sum of an array of one number', () => {
 		expect(calculator.sum([7])).toBe(7);
 	});
 
-	test.skip('computes the sum of an array of two numbers', () => {
+	test('computes the sum of an array of two numbers', () => {
 		expect(calculator.sum([7,11])).toBe(18);
 	});
 
-	test.skip('computes the sum of an array of many numbers', () => {
+	test('computes the sum of an array of many numbers', () => {
 		expect(calculator.sum([1,3,5,7,9])).toBe(25);
 	});
 });
 
 describe('multiply', () => {
-	test.skip('multiplies two numbers', () => {
+	test('multiplies two numbers', () => {
 		expect(calculator.multiply([2,4])).toBe(8);
 	});
 
-	test.skip('multiplies several numbers', () => {
+	test('multiplies several numbers', () => {
 		expect(calculator.multiply([2,4,6,8,10,12,14])).toBe(645120);
 	});
 });
 
 describe('power', () => {
-	test.skip('raises one number to the power of another number', () => {
+	test('raises one number to the power of another number', () => {
 		expect(calculator.power(4,3)).toBe(64); // 4 to third power is 64
 	});
 });
 
 describe('factorial', () => {
-	test.skip('computes the factorial of 0', () => {
+	test('computes the factorial of 0', () => {
 		expect(calculator.factorial(0)).toBe(1); // 0! = 1
 	});
 
-	test.skip('computes the factorial of 1', () => {
+	test('computes the factorial of 1', () => {
 		expect(calculator.factorial(1)).toBe(1);
 	});
 
-	test.skip('computes the factorial of 2', () => {
+	test('computes the factorial of 2', () => {
 		expect(calculator.factorial(2)).toBe(2);
 	});
 
-	test.skip('computes the factorial of 5', () => {
+	test('computes the factorial of 5', () => {
 		expect(calculator.factorial(5)).toBe(120);
 	});
 
-	test.skip('computes the factorial of 10', () => {
+	test('computes the factorial of 10', () => {
 		expect(calculator.factorial(10)).toBe(3628800);
 	});
 });