# Difference Between Node.js And The Browser JS

In this section, let's try to understand the difference between the Nodejs and Browser JS
 
-   Both the browser and Node.js use `JavaScript` as their programming language.
-   Building apps that run in the browser is a completely different thing than building a Node.js application.
-   Despite the fact that it's always JavaScript, there are some key differences that make the experience radically different.

From the perspective of a `frontend developer` who extensively uses JavaScript, Node.js apps bring with them a huge `advantage`: the comfort of programming everything - `the frontend` and `the backend `- in a `single language`.

> Javascript - the comfort of programming everything - the frontend and the backend - in a single language.

You have a huge opportunity because we know how hard it is to fully, deeply learn a programming language, and by using the same language to perform all your work on the web - both on `the client` and on `the server`, you're in a unique position of advantage.

What changes in the ecosystem.
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In the `browser`, most of the time what you are doing is interacting with the `DOM` (Document Object Model), or other Web Platform APIs like `Cookies`. Those `do not exist in Node.js`, of course. You don't have the `document`, `window` and all the other objects that are provided by the `browser`.

And in the browser, we don't have all the `nice APIs` that `Node.js` provides through its `modules`, like the `filesystem` access functionality.

Another `big difference` is that in Node.js you control the environment. Unless you are building an `open source` application that anyone can deploy anywhere, you know which version of Node.js you will run the application on. Compared to the browser environment, where you don't get the luxury to choose what browser your visitors will use, this is very convenient.

This means that you can write all the modern `ES6-7-8-9` JavaScript that your Node.js version supports.

Since JavaScript moves so `fast`, but browsers can be a bit slow and users a bit slow to upgrade, sometimes on the web, you are stuck with using older JavaScript / ECMAScript releases.

You can use `Babel` to transform your code to be `ES5-compatible` before shipping it to the browser, but in Node.js, you won't need that.

Another difference is that Node.js uses the `CommonJS module system`, while in the browser we are starting to see the `ES Modules` standard being implemented.

In practice, this means that for the time being you use `require()` in Node.js and import in the browser.

`So In this section, we saw some major differences between the Javascript running on Browser and Javascript Running on Server Side`.