Variable scope in JavaScript

This post is continuation of the series of posts on Modular approach in JavaScript

Now we have idea of writing the clear and organized code in JavaScript which is our starting point. In this post, I will be coming the variable scope in JavaScript.

In JavaScript, variable scope can be global or local. Scope is determined by where a variable is declared, and to some extent whether the var keyword is used. By default all variables defined in JavaScript are in global scope or in window scope.

Example 1:       Declaring variable in outer scope and modifying within function

Variables defined in global scope or outside functions are always available anywhere in the application until re-declared or modified.

Example 2:       Declaring variable in outer scope, but declaring again within function

If any variable is re-declares in local scope of the function then the closest variable in the scope will be accessible to the function.

Example 3:       Declaring variable within function and accessing it in outer scope

Variables declared within functions will not be accessible outside the function unless declare in outer scope.

Note: There is no such thing as Scope block {} in JavaScript. 

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