Console Learner — An interactive JavaScript course.

5.6 Further Reading

Lots of topics have been omitted from this course. Here are a few important ones:

• Block scoped variables. Using let and const to declare variables.
• Template strings. Using template literals to format strings.
• Getter and setters. Using get and set functions for dynamically computed properties.
• Iterators and generators. Using function*, yield and more to dynamically create iterables.
• Workers. How to use web workers to run code, handle notifications, etc. in the background.
• Modules. How to organize code in modules when building larger programs.

Language & Standard Library Reference

The Mozilla JavaScript Reference has been used throughout this course, as it has been a reliable and up-to-date reference for a long time. Make sure to also check their reference pages for other web technologies and browser API:s.

Debugging & Logging

Most browsers have built-in developer tools for JavaScript now. These all support logging via the console.log() API. A number of services are available for remote logging, i.e. sending the log output and browser errors to a remote server.

Performance Myths

There are lots poor recommendations and myths for optimizing JavaScript performance. Most such advice should just be ignored.

If your code has real performance issues, you or your users will notice. Make sure to use a profiler and benchmark any optimization before blindly following anyones advice.

Memory & Garbage

JavaScript is a garbage collecting language, so memory is mostly handled automatically. But note that the HTML DOM objects (wrapping web page elements) are very prone to cause memory leaks, i.e. memory that cannot be reclaimed by the garbage collector. Use profiling to find these if it becomes an issue and avoid the following:

• Circular references between an object and an HTML DOM node. Use jQuery.data() API or similar to avoid such issues.
• Long-lived closures (function scopes) with a reference to an HTML DOM node. Any function that returns another function is susceptible to these kind of issues.

Legacy Browsers

Legacy browser support has been a recurring headache for any web technology, including JavaScript. Nowadays, extensive feature and API compatibility data is available both from Mozilla JavaScript Reference and caniuse.com. And modern tools like Babel and others provide support for transpilation and polyfills to allow writing source code that takes advantage of the most recent language features.

Minification

Since JavaScript is executed in web browsers, some efficiency and protection advantages can be had by minification of the source code. The available tools have varied greatly over the years. But at the time of this writing (2023), using esbuild or swc seems like great choices.

Security

The topic of web browser security is large and better explained elsewhere. Worth noting here though, is that JavaScript does not provide any particular security mechanisms. Any code that is imported into a web page (e.g. via the <script> element) is granted full access to the global scope variables, HTTP cookies and more. This requires a high degree of trust.

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