JavaScript is a very popular and universally used programming language on the web. It is an interpreted language, which means that the code runs directly in the user's browser, without the need for a compiler. JavaScript is commonly used to add interactivity to web pages, such as animations, forms, and handling dynamic content. In this chapter, we'll explore the basics of JavaScript.
1. Basic Syntax
The syntax of JavaScript is quite similar to other C-like programming languages such as Java and C++. JavaScript code is made up of instructions that are executed by the browser. Each statement is called a 'declaration' and is separated by a semicolon (;).
For example, the statement 'var x = 5;' creates a new variable called 'x' and assigns it the value 5.
2. Variables
Variables are used to store data that can be used and manipulated in code. In JavaScript, you can declare a variable using the keywords 'var', 'let' or 'const'.
The 'var' keyword is used to declare a variable that can be changed later. 'let' is similar to 'var' but has some subtle differences that will become more evident when you learn about variable scope. 'const' is used to declare a variable whose value cannot be changed.
3. Data Types
JavaScript has several data types, including numbers, strings, Booleans, objects, null, and undefined. Numbers can be integers or decimals. Strings are sequences of characters and are enclosed in single or double quotes. Booleans represent a true or false value. Objects are collections of property and value pairs. Null is a special value that represents 'nothing' or 'empty'. Undefined means that a variable has been declared but has not yet been assigned a value.
4. Operators
Operators are used to perform operations on variables and values. JavaScript has several types of operators, including arithmetic operators like +, -, *, / and %, assignment operators like =, +=, -=, *= and /=, comparison operators like ==, !=, < , >, <= and >=, and logical operators like && (and), || (or) and ! (no).
5. Control Structures
Control structures are used to control the flow of code execution. This includes conditional statements like 'if', 'else' and 'switch', and loops like 'for', 'while' and 'do while'.
6. Functions
Functions are blocks of code that can be defined and called by name. They can have parameters, which are variables that are passed to the function when it is called, and they can return a value. Functions are key to avoiding code repetition and organizing code in a logical way.
In summary, JavaScript is a powerful and versatile programming language that is fundamental to the modern web. This was just a glimpse of the basics of JavaScript, but there's so much more to learn. As you continue to explore JavaScript, you'll discover that it is capable of much more than just adding interactivity to web pages. In fact, with the advent of Node.js, JavaScript can now be used to develop full server applications, making it a truly universal language.
