Before ES6 (2015), JavaScript variables had only Global Scope and Function Scope. ES6 introduced two important new JavaScript keywords: let and const. These two keywords provide Block Scope in JavaScript. Variables declared inside a { } …

All JavaScript variables must be identified with unique names. These unique names are called identifiers . Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).

Normally, when you create a variable inside a function, that variable is local, and can only be used inside that function. To create a global variable inside a function, you can use the global keyword.

JavaScript Global Variables. If you assign a value to a variable that has not been declared, it will automatically become a GLOBAL variable:

All variables used in a function should be declared as local variables. Local variables must be declared with the var , the let , or the const keyword, otherwise they will become global variables.

Global Variables. Variables that are created outside of a function are known as global variables. Global variables can be used by everyone, both inside of functions and outside.

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JavaScript variables can belong to: The local scope or The global scope. Global variables can be made local (private) with closures. Closures makes it possible for a function to have "private" variables.

The JavaScript global properties and methods can be used with all JavaScript objects.

The var statement declares a variable. Variables are containers for storing information. Creating a variable in JavaScript is called "declaring" a variable: