What is var, let, const in javaScript

What are Variables?

Variables are containers for storing data (storing data values).

3 Ways to Declare a JavaScript Variable

• Using var
• Using let
• Using const

When to Use JavaScript var?

• Always declare JavaScript variables with var,let, orconst.
• The var keyword is used in all JavaScript code from 1995 to 2015.
• The let and const keywords were added to JavaScript in 2015.
• If you want your code to run in older browsers, you must use var

When to Use JavaScript const?

• If you want a general rule: always declare variables with const.
• If you think the value of the variable can change, use let.

JavaScript Identifiers ?

All JavaScript variables must be identified with unique names.
These unique names are called identifiers.
JavaScript identifiers are case-sensitive.

The general rules for constructing names for variables (unique identifiers) are:

• Names can contain letters, digits, underscores, and dollar signs.
• Names must begin with a letter.
• Names can also begin with $ and _ (but we will not use it in this tutorial).
• Names are case sensitive (y and Y are different variables).
• Reserved words (like JavaScript keywords) cannot be used as names.