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Showing posts from March, 2012

JavaScript Function Spaghetti Code

In this post we will have a look at the spaghetti code created by functions and how to avoid them. First lets quickly go through why this is a cause of concern.

Problems with Function Spaghetti Code

Variables/ functions are added to the global scope
The code is not modular
There's potential for duplicate function names
Difficult to maintain
No namespace sense.
Let's take for example the following set of functions and check whats the issue with them.
// file1.js
function saveState(obj) {     // write code here to saveState of some object     alert('file1 saveState'); }
// file2.js (remote team or some third party scripts) function saveState(obj, obj2) {      // further code...     alert('file2 saveState"); }
Now the problem here is if your application is using saveState() then the execution of saveState() which one to call is determined by the script loading.  The later script overrides same functions already defined by earlier script.
For e.g.

If this script is refer…

JavaScript - The this keyword

"this" is one of the most misunderstood construct in JavaScript.  To understand this first lets go through how to create a construction function in JavaScript.  A constructor function is a function which is used to create instances of objects in JavaScript.

You define a constructor function using the same notation that you use to define a normal JavaScript function.  The convention to follow is to capitalize the first letter of the function name.

This requirement is not enforced by the JavaScript language but it is a generally accepted practice and there are many benefits which we will shortly discuss.

Let's define a constructor function to hold our menu information.

function Menu() { }
So, in the above snippet you have a constructor function named Menu defined. At present this function doesn't do anything good.

Let's see how to invoke this function

var menu = new Menu();
Let's add some public properties to this function.
function Menu() { this.menuName = &q…

JavaScript Scope

In this blog post we will dig deeper into various aspects of JavaScript scope.  This is a pretty interesting topic  and also a topic which confuses many beginning JavaScript programmers.

Understanding JavaScript scope helps you write bug free programs (hmm.. atleast helps your troubleshoot things easily)

Scope control the visibility and lifetimes of variables and parameters.  This is important from the perspective of avoiding naming collisions and provides memory management service.

Unlike other languages, JavaScript does not have block level scope.  For e.g. take for instance the following piece of c# code.
public void Main () {
int a = 5;
if (true) {
int b = 10;
// This will throw compile time error as b is not defined
// and not within the scope of function Main();
If you write the same code in JavaScript, then the value of 'b' will be available outside the 'if' block. The reason for this is JavaScript does not have block…


Hoisting is one of the feature in JavaScript that puzzles many beginners and intermediate developers.  Hoisting is a feature wherein all the variables are moved to the outermost scope, which is function, in JavaScript.  This may sometimes result in seemingly strange behavior.

Before and after hoisting

The output of the above program is an alert with a value of 10.  Traditional logic would have lead us to believe that the value of alert should be undefined.  But because of hoisting the variable is moved to the top of function declaration.  Its important to realize that only the variable declaration is moved and not the initialization.
Recommendation: Always declare your variables at the top of the function scope.
Similar to variable hoisting we also have function hoisting.  Function hoisting has different behaviors based on the fact if the function is an expression or a declaration.

A function is an expression if it is assigned to a variable.  The assignment may also hold an anonymous…

JavaScript for Web and Library Developers

This is my first blog post on my home domain and in this series of posts I will explore various facets of JavaScript language that will help us become better programmers.  The idea is tear apart the language and understand how to use the features and build libraries like jquery, knockoutjs, backbonejs.

The idea is not to replicate this libraries, but understand the inner workings using better JavaScript coding practices, design principles and thereby make the web a better place to visit..

We will be covering the following topics, though not in order and there may be addition to this list.

this keyword
Anonymous function
Server side JavaScript

Hope you will enjoy this journey with me!