In this lesson, you will learn how to use view and interpret the garbage collection activity of your node.js app via the console. You will also learn how to take heapdump snapshots and analyze them with Chrome Developer Tools to identify possible memory leaks. A sample app with a known memory leak is provided as part of the walk-through to illustrate how to use the tools in your own environments.
In this lesson, you will learn what an EventEmitter is and how it works. We start with a simple example creating an instance of the EventEmitter class, then expand on it by building listeners and emitting events to trigger them. You will learn how to view listeners in the global emitter object, as well as how to remove them and understand what the EventEmitter memory leak message means. We wrap everything up by examining the http server class to illustrate how node.js uses EventEmitters in many places for core features.
When web scraping, you'll often want to get more than just one page of data. Xray supports pagination by finding the "next" or "more" button on each page and cycling through each new page until it can no longer find that link. This lesson demonstrates how to paginate as well as more advanced selectors for when links are difficult to scrape.
npm run allows you to configure scripts inside of your
package.json file which can access locally installed node packages. If you're comfortable with this technique, you can also grunt, gulp, or other build tools by customizing your scripts and saving them inside of your
package.json file. With this approach, when a developer starts a new project with your
package.json, they can simply run
npm install then
npm run yourscript without having to install any node packages globally.