JavaScript is undoubtedly one of the most important programming languages today. The rise and evolution of the internet have aided JavaScript in scaling to an exponential level. The language has had several releases over the last two decades, and with continuous additions and deletions, there's a lot to keep up with.
If you wish to learn JavaScript and are overwhelmed with the vast content, this article on Learn JavaScript will help you. For your convenience, we have classified the concepts into four categories, they are:
- Fundamentals
- Advanced Level
- Web platform concepts
- Other tools and frameworks
Now that you know what’s in store for you let’s begin and examine these concepts in detail -
Fundamentals of JavaScript
Every language has some core concepts that dictate the basic working principle. Below is the list of such fundamental concepts that you should familiarize yourself with.
Variables
Variables are what make up a big part of JavaScript. These variables hold data like numbers to objects.
var myVariable = "This is a variable!";
Functions
Functions in JavaScript provide organized, reusable code to perform a set of actions. Functions simplify the coding process, prevent redundant logic, and make code easier to follow. This topic describes the declaration and utilization of functions, arguments, parameters, return statements, and scope in JavaScript.
Some of the concepts in Functions that you must be familiar with are -
- Function expressions
- Function() constructor
- Self-invoking functions
- Functions as values
- Functions as objects
- Arrow functions
- Generator function
- Predefined functions
Arrays
Arrays in JavaScript are defined as the data type capable of storing a list of values. JavaScript array objects are stored as variables and you can deal with them in the same way you’d deal with any other data type. Other important topics include Array Operations, Array Methods, Map, Reduce, and Filter.
var realArray = ['a', 'b', 'c'];
Loops
A loop is identified as a programming construct that is capable of repeatedly executing a piece of code. Loops as constructs, are simple yet extremely powerful. The types of loops that you need to be familiar with are -
- The for loop
- The for-in loop
- The for-of loop
- The while loop
- The do-while loop
for (var i = 0; i < 100; i++) { console.log(i); }
Objects
A JavaScript object is like a real-world entity having a state and behavior. It’s helpful if you’re familiar with creating objects, object properties, methods, and accessors.
Data Types
You must be familiar with data types like String, Bool, Numbers, Objects, Functions, Undefined. The typeof function is commonly used to find the type of the variable.
Type Conversions
As the name suggests, this includes converting one data type to another. Different types of conversions could include
- Implicit conversions
- Converting a string to a number and vice versa
- Converting an array to a string and vice versa
- Primitive to primitive conversions
- Integer to float and vice versa etc.
Control Flow
Understanding the working of common programming constructs like if, if..else, nested ifs, continue, break, etc. is crucial.
Dates
This includes creating dates, formatting JavaScript dates, increasing a date object, getting the current date and time, etc.
Operators
Operators include Logical operators, Arithmetic operators, Comparison operators, Null and Undefined, Quality and Inequality check, etc.
Scope
When a function is declared, variables in the context of its declaration are captured in its scope. Understanding local and global variables and how they can be accessed within and outside a function is important.
Once you’ve laid your foundation strong, you can go ahead and work on more advanced topics.
Advanced Level
Callbacks
Callbacks offer a way to extend the functionality of a function without changing its code. This approach is frequently used in modules (libraries/plugins), the code of which is not supposed to be changed.
Promises
A Promise object represents an operation that has produced or will eventually produce a value. Promises provide a robust way to wrap the result of asynchronous work, mitigating deeply nested callbacks.
Async Await
Async and Await are built on promises. This makes asynchronous or callback code much easier to maintain. This concept is important to understand asynchronous programming in JavaScript.
Prototypes
A prototype inherits the properties, including the methods and the variables declared in the class.
Inheritance
Inheritance works in other object-oriented languages: methods defined on the superclass are accessible in extending the subclass.
Regular Expressions
A JavaScript Regular Expression is a sequence of characters that constitutes a search pattern. These expressions define what needs to be searched in a text.
Event Loops
This is a common concept in computer programming which essentially means that your program continually waits for new things to happen, and when they do, reacts to them.
Getters and Setters
Setters and getters are object properties that call a function when they are set/gotten.
Now that you are familiar with a few advanced topics that you must know, let’s look at some web platform tools.
Web Platform Tools
Cookies
We are certain that you’re aware that Cookies let you store user information on web pages. You must know how to create, read, update, and delete cookies.
Web/Local Storage
The local storage object provides persistent (but not permanent) key-value storage of strings. It is vital to know how data is being stored.
Application Programming Interface
APIs define how to extend functionalities to the browser. There are several ones like Selection API, Notification API, Fluen API, Web cryptography APIs, and so on.
The Fetch API
This particular API is an important one. It is used to request resources.
Document Object Model
It is an object-oriented representation of structured documents like XML and HTML. It is the DOM that ensures data consistency. Understanding DOM and how DOM manipulation works is important.
Web Worker
A web worker is an easy way to run scripts in background threads as the worker thread can continue performing tasks without interfering with the user interface. A good hold of this is also essential.
Now, let’s have a look at a few JavaScript frameworks and libraries that are useful for front-end development
Other JavaScript Tools
React, Angular, Vue
React, Angular and Vue are popular JavaScript libraries and frameworks used to create interactive user interfaces for websites. It’s not necessary to learn all the three, however, React is more widely used.
TypeScript
TypeScript defines a set of types to JavaScript, which helps users write JavaScript code that is easier to understand. All of the TypeScript code compiles with JavaScript and can run smoothly on any platform.
Electron
This framework enables you to create desktop applications with JavaScript, HTML, and CSS.
JQuery
jQuery is a lightweight, "write less, do more", JavaScript library. The purpose of jQuery is to make it much easier to use JavaScript on your website. It does so by simplifying Ajax calls and DOM.
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Next Steps
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