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What does it mean 'JavaScript is interpreted'?

05/20/2022✲Tomasz Szewczyk

The IT world is complicated, full of jargon and advanced technical terms. For people not aware of sophisticated details developers language sounds like a never ending stream of magic spells. On the other hand, developers find it hard to describe complex systems using simple words. To help you find yourself in the overwhelming world of IT, I created a series of posts addressing the most important attributes of most significant programming languages.

What is JavaScript?

JavaScript is an immensely popular and rather well thought of general purpose programming language. Throughout the area of web development it is close to monopolists. The only other language competing with JavaScript is TypeScript, but in fact, it is only an extension of JavaScript.

Mobile apps and backend solutions can be developed in JavaScript as well. In these fields, developers value JavaScript for fast start-up and portability.

When speaking about JavaScript it is especially important to distinguish it from Java. Actually, they have very little in common, apart from the name.

Most important JavaScript’s attributes could be described in a few short technical terms, which sounds very mysterious for people without experience in the IT world. All of those attributes can be explained in a more straightforward way, using some clever analogies.

Full size JavaScript logo

JavaScript is interpreted

JavaScript is an interpreted programming language. Sometimes, it is called a script which is a shorthand for an interpreted programming language. Its name originates from that fact. By contrast, Java is a compiled programming language. Compiled is the opposite of interpreted.

Programs written in an interpreted programming language are executed directly using code written by the developer. A computer cannot understand JavaScript directly, hence you need an interpreter as an intermediary.

To run JavaScript code you need an interpreter, sometimes called an engine. It translates your code into simple instructions, which can actually be executed by the processor. JavaScript engines are embedded into all modern web browsers. JavaScript programs can be run without a browser using Node interpreter.

Because JavaScript programs cannot be run directly on the CPU, they are slightly slower in comparison to ones written in compiled programming languages. Fortunately, the difference is negligible in most day-to-day use cases. Throughout the area of JavaScript most common applications, the most important features are: scalability, start-up time and support for asynchronous programming. Apart from that, if you really need great performance from your JavaScript application, you can integrate some modules written in faster language into it.

Last but not least, JavaScript requires the interpreter to be present on the target platform. It is available on all major kinds of computers and operating systems, thanks to JavaScript's massive popularity. The requirement is worth noting, when you consider writing in JavaScript for some niche, less popular platforms like embedded systems.

JavaScript code on computer screen

Summary

JavaScript is one of the most popular modern programming languages. If you have any contact with the IT world, you will surely stumble upon JavaScript at some point in time. I believe my guide will help you understand JavaScript characteristics and how it differs from other programming languages.

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