Skip to main content

JavaScript: Experimenting with Conditional Statement

When conditional statement in your application grow to 30 lines or more, then it’s time for code refactoring. Conditional statements are un-avoidable but JavaScript functional programming behavior gives you really good way to handle such kind of scenario. 

Just take a scenario where you have to write a function which return sound for the given animal.

var soundOf = function(animal){
 var sound;
 if(animal === 'dog'){
  sound = 'bark';
 } else if(animal === 'duck'){
  sound = 'quack quack';  
 } else if(animal === 'owl'){
  sound = 'hoot';  
 } else {
  sound = 'animal not found!!!';
 return sound;

Now think, what your code look like when you have to support 100 animal !!!
And same will be true for switch-case statement

var soundOf = function(animal){
 var sound;
  case 'dog': 
   sound = 'bark'; 
  case 'duck': 
   sound = 'quack quack'; 
  case 'owl': 
   sound = 'hoot'; 
   sound = 'animal not found!!!';
 return sound;

Here is my preferred way to write same function

var soundOf = function(animal){
 var animalSound = {
   dog: 'bark',
   duck: 'quack quack',
   owl: 'hoot' 
  animalNotFound = 'animal not found!!!';
 return (animalSound[animal] || animalNotFound);

It’s look very clean and easy to understand. You can easily update this function with minimal changes to support more animals.


soundOf('dog');  //'bark'
soundOf('owl');  //'hoot'
soundOf('tiger'); //'animal not found!!!'
soundOf('duck'); //'quack quack'

You can use same pattern for some more complex task

var format = function(){
 function dateFormatter(value) {
  //code to format date
  return 'date: ' + value;
 function numberFormatter(value) {
  //code to format number
  return 'number: ' + value;
 function stringFormatter(value) {
  //code to format string
  return 'string: ' + value;
 function formatterNotFound(){
  return 'un-known data type!!!';
 var formatterMapping = {
  date : dateFormatter,
  number : numberFormatter,
  string : stringFormatter 
 return function(type, value){
  return (formatterMapping[type] || formatterNotFound)(value);


format('date','19-03-2012')  //'date: 19-03-2012'
format('number','123')   //'number: 123'
format('float','321.123')  //'un-known data type!!!'

Popular posts from this blog

ERROR: Ignored call to 'alert()'. The document is sandboxed, and the 'allow-modals' keyword is not set.

Recently I found this issue while writing code snippet in "JSFiddle". And after searching, found this was happening because of new feature added in "Chrome 46+". But at the same time Chrome doesn't have support for "allow-modals" property in "sandbox" attribute.

Chromium issue for above behavior:

To make it work you have to add "allow-scripts allow-modals" in "sandbox" attribute, and use "window.alert" instead of "alert".

<!-- Sandbox frame will execute javascript and show modal dialogs --> <iframe sandbox="allow-scripts allow-modals" src="iframe.html"> </iframe>

Feature added: Block modal dialog inside a sandboxed iframe.

Feature working Demo page:

CSS Specificity

Many time different CSS rules overlap on one or more element. And some people always get confuse about, which rule will take higher priority then other and why? CSS Specificity is the answer of all these kind of questions.
As the name suggest, the CSS rule which is more specific to the element will take higher priority then other. Means something like “#some_id{}” will always take higher priority then “*{}” universal selector.  And if duplicate rules are define then the last rule will be applied to the element.

The following list of selectors is by increasing specificity:
Type selector (e.g., div) and pseudo-elements in selector (e.g., :after) Class selectors (e.g., .some_class), attributes selectors (e.g., [type=”radio”]) and pseudo-class selector (e.g., :hover) Id selectors (e.g., #some_id)

ID takes higher priority then Class, Type and Universal selector (Note: Universal selector has no effect on specificity, see below special conditions). 

If duplicate rules are given, then last…

Guava: Some useful IO utilities

Guava IO package provides very useful utility classes for input/ouput stream, byte stream, file handling and many more. Here are few example which show case how these utilities can make your code much cleaner, modular and more readable.Copy “InputStream” to “OutputStream InputStream is = CopyStreams.class.getResourceAsStream("test.txt"); OutputStream os = System.out; ByteStreams.copy(is, os);Changing InputStream to “byte[]” InputStream is = CopyStreams.class.getResourceAsStream("test.txt"); byte[] isBytes = ByteStreams.toByteArray(is); // Now if you want to get base64 encoded string then it will be like this String isBase64Str = new sun.misc.BASE64Encoder().encode(isBytes);Combining two files in one File input1 = new File("c:\\testio\\AWords.txt"); File input2 = new File("c:\\testio\\BWords.txt"); File output = new File("c:\\testio\\ABWords.txt"); …