Book Image

Professional JavaScript

By : Hugo Di Francesco, Siyuan Gao, Vinicius Isola, Philip Kirkbride
Book Image

Professional JavaScript

By: Hugo Di Francesco, Siyuan Gao, Vinicius Isola, Philip Kirkbride

Overview of this book

In depth knowledge of JavaScript makes it easier to learn a variety of other frameworks, including React, Angular, and related tools and libraries. This book is designed to help you cover the core JavaScript concepts you need to build modern applications. You'll start by learning how to represent an HTML document in the Document Object Model (DOM). Then, you'll combine your knowledge of the DOM and Node.js to create a web scraper for practical situations. As you read through further lessons, you'll create a Node.js-based RESTful API using the Express library for Node.js. You'll also understand how modular designs can be used for better reusability and collaboration with multiple developers on a single project. Later lessons will guide you through building unit tests, which ensure that the core functionality of your program is not affected over time. The book will also demonstrate how constructors, async/await, and events can load your applications quickly and efficiently. Finally, you'll gain useful insights into functional programming concepts such as immutability, pure functions, and higher-order functions. By the end of this book, you'll have the skills you need to tackle any real-world JavaScript development problem using a modern JavaScript approach, both for the client and server sides.
Table of Contents (12 chapters)

Handling Large Files in Node.js

In the previous exercise, we went over how we can use the fs module to read file contents in Node.js. This works well when we are dealing with small files that are smaller than 100 MB. When we are dealing with large files (> 2 GB), sometimes, it is not possible to read the entire file using fs.readFile. Consider the following scenario.

You are given a 20 GB text file and you need to process the data in the file line by line and write the output into an output file. Your computer only has 8 GB of memory.

When you are using fs.readFile, it will attempt to read the entire content of the file into the computer's memory. In our case, this won't be possible because our computer does not have enough memory installed to fit the entire content of the file we are processing. Here, we need a separate approach to this problem. To process large files, we need to use streams.

The stream is an interesting concept in programming. It treats data...