Added factorial to coding challenges.

Author: ratracegrad

factorial/factorial.js

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+/***************************************************************
+ *                                                             *
+ *                       CodePrep.io                           *
+ *                                                             *
+ *   Function:  factorial(num)                                 *
+ *   Input:    1 number parameter                              *
+ *   Output:   number                                          *
+ *                                                             *
+ *   Output expectations:                                      *
+ *   var myTest = factorial(4);                                *
+ *   console.log(myTest);  // 24                               *
+ *                                                             *
+ *   Factorial is the product of an integer and all the        *
+ *   integers below it. For example the factorial of 4 is      *
+ *   24 which is 4 * 3 * 2 * 1.                                *
+ *   Write the code for the factorial function that            *
+ *   takes a number as input and then outputs a number.        *
+ *                                                             *
+ **************************************************************/
+
+var factorial = function(num) {
+    /* YOUR CODE GOES HERE */
+
+}

factorial/factorial.test.js

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+var should = require('should');
+var vm = require('vm');
+var fs = require('fs');
+var filename = __filename.replace(/\.test\.js$/, '.js');
+vm.runInThisContext(fs.readFileSync(filename), filename);
+
+describe('Factorial', function() {
+    it('should exist', function(){
+        should.exist(factorial);
+    });
+
+    it('should be a function', function() {
+        factorial.should.be.a.Function;
+    });
+
+    it('should return a number', function() {
+        var result = factorial(4);
+        should.exist(result);
+        result.should.be.an.instanceof(Number);
+    });
+
+    it('should return 1 for factorial of 1', function(){
+        var result = factorial(1);
+        result.should.be.eql(1);
+    });
+
+    it('should return 6 for factorial of 3', function(){
+        var result = factorial(3);
+        result.should.be.eql(6);
+    });
+
+    it('should return 362880 for factorial of 9', function(){
+        var result = factorial(9);
+        result.should.be.eql(362880);
+    });
+
+});

factorial/package.json

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+{
+  "name": "CodePrep.io_coding_challenges",
+  "author": "Jennifer Bland",
+  "url": "http://www.codeprep.io",
+  "version": "1.0.0",
+  "description": "CodePrep.io presents coding challenges you might face when interviewing for a Full-Stack Developer position",
+  "scripts": {
+    "test": "node ../node_modules/mocha/bin/mocha ./*.test.js"
+  }
+}