[UPDATE] implementation, tests, example

README.md

@@ -2,7 +2,7 @@ nanprod
 ===
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-> Computes the product over an array of values ignoring any values which are not numeric. 
+> Computes the product over an array of values ignoring any values which are not numeric.
 
 
 ## Installation
@@ -16,19 +16,40 @@ For use in the browser, use [browserify](https://github.com/substack/node-browse
 
 ## Usage
 
+To use the module,
+
 ``` javascript
-var foo = require( 'compute-nanprod' );
+var nanprod = require( 'compute-nanprod' );
 ```
 
-#### foo( arr )
+#### nanprod( arr )
+
+Computes the product while ignoring non-numeric values.
 
-What does this function do?
+``` javascript
+var data = [ 1, NaN, 2, NaN, 1 ];
 
+var product = nanprod( data );
+// returns 2
+```
 
 ## Examples
 
 ``` javascript
-var foo = require( 'compute-nanprod' );
+var nanprod = require( 'compute-nanprod' );
+
+var data = new Array( 10 );
+
+for ( var i = 0; i < data.length; i++ ) {
+	if ( i%5 === 0 ) {
+		data[ i ] = NaN;
+	} else {
+		data[ i ] = Math.random() + 1;
+	}
+}
+
+console.log( nanprod( data ) );
+
 ```
 
 To run the example code from the top-level application directory,
@@ -38,6 +59,19 @@ $ node ./examples/index.js
 ```
 
 
+## Notes
+
+The product of an array containing non-numeric values is equal to the product of an equivalent array which contains only the numeric values. Hence,
+
+``` javascript
+var d1 = [ 1, NaN, 2, 3, NaN ],
+    d2 = [ 1, 2, 3 ];
+
+console.log( nanprod( d1 ) === nanprod( d2 ) );
+// returns true
+```
+
+
 ## Tests
 
 ### Unit
@@ -69,7 +103,7 @@ $ make view-cov
 ---
 ## License
 
-[MIT license](http://opensource.org/licenses/MIT). 
+[MIT license](http://opensource.org/licenses/MIT).
 
 
 ## Copyright

examples/index.js

@@ -1,3 +1,15 @@
 'use strict';
 
-var module = require( './../lib' );
+var nanprod = require( './../lib' );
+
+var data = new Array( 10 );
+
+for ( var i = 0; i < data.length; i++ ) {
+	if ( i%5 === 0 ) {
+		data[ i ] = NaN;
+	} else {
+		data[ i ] = Math.random() + 1;
+	}
+}
+
+console.log( nanprod( data ) );

lib/index.js

@@ -4,7 +4,7 @@
 *
 *
 *	DESCRIPTION:
-*		- Computes the product over an array of values ignoring any values which are not numeric. 
+*		- Computes the product over an array of values ignoring any values which are not numeric.
 *
 *
 *	NOTES:
@@ -35,15 +35,34 @@
 
 // FUNCTIONS //
 
+// NANPROD //
 /**
-* FUNCTION: foo()
-*	{{ foo description }}.
+* FUNCTION: nanprod( arr )
+* Computes the product over an array of values ignoring non-numeric values.
+*
+* @param {Array} arr - array of values
+* @returns {Number} prod
 */
-function foo() {
+function nanprod( arr ) {
+  if ( !Array.isArray( arr ) ) {
+    throw new TypeError( 'nanprod()::invalid input argument. Must provide an array.' );
+  }
+  var len = arr.length, p = 1, val;
 
-} // end FUNCTION foo()
+  for ( var i = 0; i < len; i++ ) {
+    val = arr[ i ];
+    if ( typeof val !== 'number' || val !== val ) {
+      continue;
+    }
+    p *= val;
+    if (p === 0){
+      break;
+    }
+  }
+  return p;
+} // end FUNCTION nanprod()
 
 
 // EXPORTS //
 
-module.exports = foo;
+module.exports = nanprod;

test/test.js

@@ -7,7 +7,7 @@ var // Expectation library:
 	chai = require( 'chai' ),
 
 	// Module to be tested:
-	lib = require( './../lib' );
+	nanprod = require( './../lib' );
 
 
 // VARIABLES //
@@ -21,9 +21,47 @@ var expect = chai.expect,
 describe( 'compute-nanprod', function tests() {
 
 	it( 'should export a function', function test() {
-		expect( lib ).to.be.a( 'function' );
+		expect( nanprod ).to.be.a( 'function' );
 	});
 
-	it( 'should do something' );
+	it( 'should throw an error if provided a non-array', function test() {
+		var values = [
+				'5',
+				5,
+				true,
+				undefined,
+				null,
+				NaN,
+				function(){},
+				{}
+			];
+
+		for ( var i = 0; i < values.length; i++ ) {
+			expect( badValue( values[i] ) ).to.throw( TypeError );
+		}
+		function badValue( value ) {
+			return function() {
+				nanprod( value );
+			};
+		}
+	});
+
+	it( 'should compute the product', function test() {
+		var data, expected;
+
+		data = [ 2, 4, NaN, 5, 3, 8, NaN, 2 ];
+		expected = 1920;
+
+		assert.strictEqual( nanprod( data ), expected );
+	});
+
+	it( 'terminates early if product equals zero', function test() {
+		var data, expected;
+
+		data = [ 2, 4, NaN, 0, 3, 8, NaN, 2 ];
+		expected = 0;
+
+		assert.strictEqual( nanprod( data ), expected );
+	});
 
 });