Merge pull request #1557 from wileymab/feature/code-javascript-factorial

Added Factorial in JavaScript

.gitignore

@@ -10,5 +10,6 @@ _site/
 *.swp
 .pytest_cache/
 __pycache__/
+.scratch
 # erlang
 *.beam

archive/j/javascript/README.md

@@ -9,6 +9,7 @@ Welcome to Sample Programs in JavaScript!
 - [Fizz Buzz in JavaScript][4]
 - [Baklava in JavaScript][8]
   - Solution borrowed from @toturkmen via the [baklava repo][1]
+- [Factorial in JavaScript][15]
 - [Fibonacci in JavaScript][9]
 - [Capitalize in JavaScript][12]
 - [Import in JavaScript][13]
@@ -41,4 +42,5 @@ Welcome to Sample Programs in JavaScript!
 [11]: https://www.w3schools.com/js/
 [12]: https://github.com/TheRenegadeCoder/sample-programs/issues/1067
 [13]: https://github.com/TheRenegadeCoder/sample-programs/issues/1178
-[14]: https://github.com/TheRenegadeCoder/sample-programs/issues/1191
+[14]: https://github.com/TheRenegadeCoder/sample-programs/issues/1191
+[15]: https://github.com/TheRenegadeCoder/sample-programs/issues/1383

archive/j/javascript/factorial.js

@@ -0,0 +1,53 @@
+/**
+ * Calculate the factorial of a given integer input.
+ * 
+ * @param {Integer} num 
+ */
+function factorial(num) {
+    let product = 1;
+    if ( num > 1 ) {
+        for ( let i = 2; i <= num; i++ ) {
+            product *= i
+        }
+    }
+    return product
+}
+
+/**
+ * Executable function
+ * 
+ * @param {Command line input} input 
+ */
+function main(input) {
+    // Usage text
+    const usage = 'Usage: please input a non-negative integer';
+
+    /**
+     * If we remove all the integer characters from the input and are left with
+     * an empty string, then we have a valid integer.
+     */
+    const inputValidation = input.replace(/[0-9]/g,'')
+
+    if ( inputValidation === '' ) {
+        // Valid integer
+        const parsedInput = parseInt(input)
+        if ( parsedInput < 0 ) {
+            console.log(usage)
+        }
+        else if ( parsedInput > 170 ) {
+            console.log(`Input of ${parsedInput} is too large to calculate a factorial for. Max input is 170.`)
+        }
+        else {
+            console.log(factorial(parsedInput))
+        }
+    }
+    else {
+        // Anything non integer
+        console.log(usage)
+    }
+
+}
+
+// Run the executable function
+const input = process.argv[2]
+main(input)