04. Function Scope

Depending on where a variable is declared, it may or may not be accessible in certain segments of your code. The topic that deals with this is known as scope, and there are two main descriptors of scope - local and global.

Local

A local variable is one that is created inside a function with the var keyword.

A local variable may only be accessed within its declared function.

global

A global variable is declared outside all functions, and is stored in memory as long as the web page is loaded into the web browser. Global varialbes have more overhead, since the browser has to remember them for however long the web page is loaded for.

Because a global variable is accessible to all areas in the code, there is a high risk of naming conflicts. Due to these reasons, global variables should be seldomly used.

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