Javascript is a programming language used to make web pages interactive, and forms the backbone of almost all modern websites. Knowing the basics of Javascript can be a powerful addition to any web development skillset. In this article, we’ll learn all the basics of Javascript, from the syntax and data types, through to jQuery and best practices for writing clean code.

What is Javascript?

Javascript is a scripting language used to make web pages interactive. It primarily runs client-side, meaning that the code is compiled and run locally on the user’s browser, rather than on a remote server. This lets developers do things like create dropdown menus or show animations without waiting for the server to respond. While the traditional HTML language governs the structure and content of a website, Javascript allows you to manipulate both the structure and the content.

Javascript is a powerful language that can be used to create dynamic and interactive webpages. It can be used to create games, interactive forms, and even to create applications that run in the browser. It is also used to create mobile applications, as well as to create desktop applications. Javascript is an essential language for any web developer, and is used in almost all modern web applications.

Javascript Syntax Basics

Javascript syntax uses English keywords combined with mathematical operators, like most programming languages. It uses curly braces to denote code blocks for control flow statements such as loops, functions, and conditionals. Statements are typically terminated with a semicolon. Variables are declared using either the var, let, or const keywords, depending on the scope and longevity of the variable. Variables can be either primitive or complex data types.

Primitive data types include strings, numbers, booleans, and null. Complex data types include objects, arrays, and functions. Javascript is a case-sensitive language, meaning that variables and keywords must be written in the same case as they were declared. It is also a loosely typed language, meaning that variables do not need to be declared with a specific data type.

Data Types in Javascript

Javascript supports a number of native data types such as strings, numbers, and booleans. It also supports complex data types such as objects and arrays. Objects are collections of key-value pairs useful for storing data, while arrays are best suited for storing lists of values such as numbers, strings, and objects.

In addition to these data types, Javascript also supports functions, which are blocks of code that can be executed when called. Functions are useful for performing complex operations and can be used to create reusable code snippets.

Variables in Javascript

Variables are named memory locations used to store data while a program runs. In Javascript, variables are declared with one of the three keywords – var, let, or const. Var is the traditional keyword used for most variables that hold data that changes during the execution of the program, while let is used for variables that are scoped to blocks such as loops or functions. Const is used for variables that do not change during program execution, typically for values that will be used throughout such as configuration values.

It is important to note that variables declared with the var keyword are not limited to the scope of the block they are declared in, and can be accessed from anywhere in the program. Variables declared with the let and const keywords are limited to the scope of the block they are declared in, and cannot be accessed outside of that scope.

Operators in Javascript

Operators are special symbols used to operations such as arithmetic or logic operations. Javascript supports common arithmetic operators such as addition, subtraction, multiplication and division, as well as logical operators such as comparison and Boolean operators. These are utilized to form conditional statements such as if..else or ternary expressions.

Control Flow in Javascript

Control flow statements allow developers to set up logic within programs by enacting conditionals that allow specific pieces of code to execute based on predetermined conditions. This could involve while loops and if..else blocks, or ternary expressions which are equivalent to an if..else statement in a single line. Control flow can also involve switch statements when dealing with multiple execution paths.

Functions in Javascript

Functions are blocks of code that can be called independently from another context. They are often used for repeating tasks such as looping over data structures or formatting user input. Functions typically accept one or more parameters that can be used to pass data into them from other context. Functions can be declared with either the function keyword or arrow functions.

Objects in Javascript

Objects are complex data types that contain key-value pairs representing data. These are often used to keep related data together in ways that maintain readability and make it more efficient for programs to parse. Object literals can also be created containing key-value pairs with each piece of data representing a different property of that object.

Arrays in Javascript

Arrays are similar to objects but contain a list of values rather than a set of key-value pairs. They are functionally similar but optimized for certain operations such as sorting and finding individual items from within larger datasets. Arrays can contain elements of any type, including other arrays, making them powerful tools for storing related items.

Error Handling in Javascript

Error handling is an essential part of programming and is necessary to ensure that programs function correctly no matter what the user input or external conditions may be. Javascript provides a range of built-in error handling functions such as try/catch or onerror handlers that can be used to trap errors before they manifest in production code.

jQuery and Other Libraries

jQuery is a popular library used with Javascript. It provides a number of useful functions for manipulating the DOM and simplifying common tasks such as adding event listeners or easing animations. Other libraries include React and Angular which provide frameworks for creating fully-fledged web apps using Javascript.

Best Practices for Writing Clean Code

Writing clean code is important for making programs easier to debug and maintain in future. This involves breaking large functions into smaller ones, reducing nesting depths, using descriptive variable names, avoiding unnecessary global variables, and ensuring all logic is laid out logically. Commenting code is also a great way to add context to programs for other developers to understand what’s going on without having to trawl through the code itself.

How to Debug Your Code

Debugging your code is essential in order to identify any issues before they manifest in production. This can often involve working towards an expected result step by step and running code through an IDE’s debugger or a linter such as ESLint which provides helpful warnings and errors when coding standards aren’t maintained. With these tools you can quickly identify any logic flaws or obscure syntax errors.

Tips and Tricks for Optimizing Performance

Optimizing performance involves reducing the time taken by programs to execute specific tasks such as sorting large datasets or searching large volumes of text. This can often involve writing custom algorithms tailored to the specific task at hand or using efficient data structures such as hash tables or trees when searching large datasets.

Resources for Further Learning

There are plenty of resources available for further learning Javascript. Popular websites such as Codecademy provide interactive courses so new developers can learn the basics without getting stuck on any specifics. While Reddit’s /r/javascript is great for quality discussion about projects or issues other users may have experienced. Books such as Eloquent Javascript provide an in depth coverage of the language and its capabilities.