# Hello, world! The tutorial that you're reading is about core JavaScript, which is platform-independent. Further on, you will learn Node.JS and other platforms that use it. But, we need a working environment to run our scripts, and, just because this book is online, the browser is a good choice. We'll keep the amount of browser-specific commands (like `alert`) to a minimum so that you don't spend time on them if you plan to concentrate on another environment like Node.JS. On the other hand, browser details are explained in detail in the [next part](/ui) of the tutorial. So first, let's see how to attach a script to a webpage. For server-side environments, you can just execute it with a command like `"node my.js"` for Node.JS. ## The "script" tag JavaScript programs can be inserted in any part of an HTML document with the help of the ` */!*

...After the script.

``` ```online You can run the example by clicking on the "Play" button in its right-top corner. ``` The ` ``` This trick isn't used in modern JavaScript. These comments were used to hide the JavaScript code from old browsers that didn't know about a ` ``` Here `/path/to/script.js` is an absolute path to the file with the script (from the site root). It is also possible to provide a path relative to the current page. For instance, `src="script.js"` would mean a file `"script.js"` in the current folder. We can give a full URL as well. For instance: ```html ``` To attach several scripts, use multiple tags: ```html … ``` ```smart As a rule, only the simplest scripts are put into HTML. More complex ones reside in separate files. The benefit of a separate file is that the browser will download it and then store it in its [cache](https://en.wikipedia.org/wiki/Web_cache). After this, other pages that want the same script will take it from the cache instead of downloading it. So the file is actually downloaded only once. That saves traffic and makes pages faster. ``` ````warn header="If `src` is set, the script content is ignored." A single ` ``` We must choose: either it's an external ` ``` ```` ## Summary - We can use a ``. There is much more to learn about browser scripts and their interaction with the web-page. But let's keep in mind that this part of the tutorial is devoted to the JavaScript language, so we shouldn't distract ourselves from it. We'll be using a browser as a way to run JavaScript, which is very convenient for online reading, but yet one of many.