Variables in JavaScript

• In JavaScript, variables are used to store data values that can be used in the code.
• Variables are created using the var, let, or const keywords, and they can hold different types of data, such as numbers, strings, and objects.

Here is a brief overview of the three different variable types in JavaScript:

• var variables: var variables are the original way of declaring variables in JavaScript. They are function-scoped, meaning that they are visible only within the function in which they are defined.

Example:

    function myFunction() {

        var x = 10;

        console.log(x);

    }

• let variables: let variables were introduced in ES6 (ECMAScript 2015) and are block-scoped, meaning that they are visible only within the block in which they are defined.

Example:

    if (true) {

        let x = 10;

        console.log(x);

    }

• const variables: const variables are also block-scoped, but unlike let variables, their value cannot be changed once they are defined.

Example:

    const x = 10;

    console.log(x);

    // x = 20; // This will cause an error because x is a constant

• Variables in JavaScript can also be assigned a value when they are defined, or they can be declared without a value.

• If a variable is declared without a value, it will have a value of undefined until a value is assigned to it.

Example:

    var x; // Declaring a variable without a value

    x = 10; // Assigning a value to the variable

    console.log(x); // Output: 10

• Overall, variables are a fundamental concept in JavaScript and are used extensively in programming to store and manipulate data values.