A comprehensive tutorial on using single var pattern in JavaScript

Published: Aug 02, 2015

The flexibility of JavaScript makes it one of the finest programming languages to date. Eliminating the need for following traditional sets of programming conventions, JavaScript serves as a dynamic language that continues to amaze developers. One of the best utilities available with JavaScript is the convenience of creating any type of variable, anywhere within the script.

Additionally, working with JavaScript variables becomes a complete breeze with the single var pattern. In this tutorial, I’ll be walking you through everything that is associated with the correct usage of single var pattern during web development using JavaScript.

What is the Single Var Pattern?

The single var pattern is a design that all local variables are created using a single var statement. This is usually placed towards the start of the function block. Each variable within the set of variables is separated using a comma(,) with the last variable ending with a semicolon(;) marketing the termination of var statement. Let’s look at the example below:

function customfunction() {
  var  a = 2,
       b = "Hello",
       c = { name: "James", age: 40 },
       d = new Date(),

On the contrary, have a look at the below function which includes the declaration of multiple var statements for each variable:

function customfunction() {
  var a = 2;
  var b = "Hello";
  var c = { name: "James", age: 40 };
  var d = new Date();
  var e;

In JavaScript all the newlines, spaces, tabs and a variety of spacing characters used before and after the commas and semicolons are simply ignored. So writing single var in a single line also works as well:

function customfunction() {
  var a = 2, b = "Hello", c = { name: "James", age: 40 }, d = new Date(), e;

For readability and space for comments, I prefer having each variable in its own line. But this convention is totally up to you.

Data Type is not necessary in declaring variables

Since JavaScript is a dynamically typed programming language, you don’t need to explicitly declare the data type for a particular variable. In addition, you can change this data type from one type to another easily. Which means that you’re able to have a collection of different data types in a single var statement. JavaScript doesn’t enforce strict rules for variable declaration.

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This makes this language quite powerful as well as easy to write.

Why use the Single Var Pattern?

Plenty might argue, why unlearn the conventional way of using multiple var keywords? What’s the real purpose of the Single Var pattern?

Code readability

Since a single var JavaScript pattern is quite similar to the abstract of a scientific paper, you can witness an improved code readability. That means, you can name the variables more intuitively, followed by commenting the functions appropriately.

Maintenance is easier

The single var pattern makes it convenient for you to create and manage variables. Variables are always on the top of the function for easy review. This makes it easy to remember when adding or modifying variables when working in a specific function.

Minimization of global variables

By eliminating all the global variables from your work, your project will execute safely. Global variables have been primary reasons behind naming collisions and should be avoided as much as possible. With the single var pattern, you can are encouraged to use local variables, thereby reducing the risk global variables pose.

This article is written by Jack Calder – a perfect professional in Markupcloud Ltd – a top notch company involved into convert psd to html and wordpress. Jack has shared here the views on how you can utilize the Singe variable pattern in Javascript.