Variable

In programming, a variable is a container that stores a value or a reference to a value. Variables allow programmers to manipulate and process data dynamically in their programs.

In JavaScript, variables can be declared using the var, let, or const keyword followed by a variable name. For example:

javascriptCopy codevar num = 5; // declare a variable called num and assign it the value 5
let message = "Hello, world!"; // declare a variable called message and assign it a string value
const PI = 3.14; // declare a constant variable called PI and assign it the value 3.14

In the examples above, the var, let, and const keywords are used to declare variables with different characteristics. var and let are used to declare mutable variables, meaning that their values can be changed throughout the program. const, on the other hand, is used to declare constant variables, meaning that their values cannot be changed once they are assigned.

Variables can be assigned many different types of values, including strings, numbers, booleans, arrays, objects, and functions. For example:

var age = 30;
var isMarried = true;
var hobbies = ["reading", "coding", "swimming"];
var person = { name: "Jane", age: 25, isMarried: false };
var greeting = function(name) {
  console.log("Hello, " + name + "!");
}

In the examples above, name is a string variable, age is a number variable, isMarried is a boolean variable, hobbies is an array variable, person is an object variable, and greeting is a function variable. These variables can be used throughout the program to perform various operations and calculations.