What is JavaScript
JavaScript is a high-level, dynamic programming language used primarily to create interactive effects with in web browsers. It was first introduced in 1995 by Netscape and has since become one of the most widely used programming languages in the world.
JavaScript allows developers to create interactive web pages by providing the ability to dynamically update and change the content of a web page in response to user actions, without requiring the page to be reloaded from the server. This can include things like form validation, animations, and user interface enhancements.
In addition to its use in web development, JavaScript is also widely used in server-side programming, mobile app development, game development, and other application areas. With the introduction of newer features in more recent versions of the language, such as async/await, arrow functions, and template literals, JavaScript has become an even more powerful and flexible language for developers.
What are its Variables
In JavaScript, variables are used to store values or data. They are a fundamental part of the language and are used in almost every JavaScript program.
A variable is created using the keyword “var”, “let”, or “const”, followed by the name of the variable and optionally an initial value. For example:
var myVariable = 42; // using var (older syntax)
let myOtherVariable = "Hello, world!"; // using let (recommended)
const PI = 3.14159; // using const (immutable value)The name of a variable can be any valid identifier in JavaScript, such as a word or a combination of letters and numbers, but it must follow certain rules. The initial value of a variable can be any JavaScript data type, including numbers, strings, arrays, objects, and more.
Once a variable is defined, its value can be changed or updated throughout the program. This allows JavaScript programs to be dynamic and respond to user input and other changes.
Data types
JavaScript supports several data types that can be used to represent different kinds of values. These data types include:
- Number: This data type is used to represent numeric values. It includes both integers and floating-point numbers.
- String: A string is a sequence of characters enclosed in quotes. It can be used to represent textual data.
- Boolean: A boolean data type has only two values, true or false, and is used to represent logical values.
- Undefined: This data type represents a variable that has been declared but has not been assigned a value.
- Null: Null represents a deliberate non-value, meaning that the variable has no value at all.
- Object: An object is a complex data type that can be used to represent a collection of related values, known as properties. Objects can be created using the object literal syntax, or by using a constructor function.
- Symbol: This is a unique and immutable data type introduced in ES6 that can be used to create private object properties.
JavaScript also has two additional data types called BigInt and Map, which were introduced in more recent versions of the language. BigInt is used to represent integers larger than the maximum representable by the number data type, while Map is used to represent collections of key-value pairs.
List rules for variable declaration in JavaScript.
Here are some general rules for variable declaration in JavaScript:
- Variable names must start with a letter, underscore (_), or dollar sign ($). They cannot start with a number.
- Variable names can only contain letters, numbers, underscores, or dollar signs. They cannot contain spaces or special characters like #, %, or @.
- Variable names are case-sensitive, so myVar and myvar are considered two different variables.
- JavaScript has several reserved keywords that cannot be used as variable names, such as if, for, while, and function.
- When declaring a variable, you can use the let, const, or var keywords. let and const were introduced in ES6 (ECMAScript 2015) and are block-scoped, whereas var is function-scoped.
- Use let when you need to reassign the variable to a new value, and const when you want the value to remain constant and cannot be reassigned.
- You must initialize a const variable when it’s declared; otherwise, you’ll get a syntax error.
- JavaScript is a loosely-typed language, meaning you don’t need to specify the data type of a variable when you declare it. The data type is determined dynamically when you assign a value to the variable.
- When assigning a value to a variable, you can use the = operator. For example, let x = 5; .
- Use meaningful and descriptive names for variables to make your code more readable and maintainable.
- Declare variables at the top of their scope (i.e., at the beginning of a function or block of code) to avoid hoisting issues.
- Avoid using global variables as much as possible to prevent naming collisions and maintain code clarity.
Write a JavaScript to find greater of two numbers.
var num1 = parseInt(prompt("Enter first number:"));
var num2 = parseInt(prompt("Enter second number:"));
if (num1 == num2) {
console.log(num1 + " is equal to " + num2);
} else if (num1 > num2) {
console.log(num1 + " is larger than " + num2);
} else {
console.log(num1 + " is lesser than " + num2);
}
