Node.js

You might say

The terminal says command not found: node. Why can't my project run?

The environment that lets JavaScript run directly on a computer, and the runtime behind build tools and AI dev toolsWhen running build scripts or starting modern web projects in a terminal, Node.js provides the runtime that executes JavaScript outside a browser. Beyond handling web page clicks, JavaScript runs server APIs and dev tools via Node.js; project warnings like 'requires Node 18+' mean you must verify your local runtime version first.

Know first

JavaScript

Nodenode

The same .js file, run by a browser and by Node.js

script.js

const fs = require("fs");
const files = fs.readdirSync("./data");
console.log(`Read ${files.length} item(s)`);

file:///Users/you/project/script.js

const fs = require("fs");
const files = fs.readdirSync("./data");
console.log(`Read ${files.length} item(s)`);

The browser just shows the file as text; it does not run it

JavaScript has two common runtimes: pages in a browser and Node.js in a terminal. Project commands, npm, and build tools all run on the latter.

Where Node.js sits in the toolchain

It is a runtime, not a new language: You still write JavaScript. Node.js adds the ability to execute it on a computer, so scripts run without opening a browser.

Build and package tools depend on it: npm installing dependencies, build commands, and AI development tools themselves all run on Node.js. Without it, project commands fail with command not found.

Projects require specific versions: When docs say requires Node 18+, run node -v to see the local version; upgrade before running if it is too low.

Quick checkChoose the best answer

Following project docs, running npm start reports command not found: node. What should happen next?

Open the project entry file in a browser to run itInstall Node.js, verify the version with node -v, then retryRe-clone the project and run the same command

You can say this to an AI Agent

The terminal reports command not found: node. First check whether Node.js is installed here and its version; if it is missing or below the project requirement, tell me which version to install, then rerun the project command and confirm it starts.

Learn next

1JavaScript→2Terminal→3npm→4Dependency→

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