设置开发环境（node_modules复制）

Question

(I am an Actionscript developer finally migrating to JavaScript and am learning TypeScript and AngularJS 2 . Let me know if this question is too stupid/naive and I will delete it)

I'm running through the Angular 2 tutorials and all is well but I am wondering about how one typically sets up a development environment without duplication of, for example the "node_modules" and "typings" directories. I understand that the tutorials want to be complete in themselves so there is duplication. I also get that, for example, the line below is using a reference relative to the project folder so it could point someplace else.

Is there a "best practice" for avoiding duplication of node modules? I ask because the "node_modules" directory is 145 mb.

import {Component} from 'angular2/core';

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Answer 1

node_modules being duplicated in each project is by design - the idea of having a package.json file and a corresponding folder of dependencies is so that your project is self-sufficient/isolated and does not rely on the environment it's being used in.

That said, you can install NPM modules globally using the npm install [package] -g command, but here's a practical example of why you probably shouldn't - say you have an ongoing project that uses an old version of Angular 2, and you want to start a second project using the latest features. If you're using a global Angular install, this isn't possible; updating the version would update it for every project that's using it (which could horribly break your old app). If you have a separate install per-project, their versions can be different without causing any issues.

This also comes in handy when committing your project to version control - if your entire app relies on globally installed modules and you (or a contributor) wants to work on it on another machine, they'll have to go through and install every single dependency manually so that the environment matches the one it was originally developed in. Compare this to having your dependencies listed in package.json and your node_modules folder excluded from the repo - they just have to run npm install and NPM will install all the relevant modules for them.

I admit that the size of node_modules can get excessive at times, and I hope they optimize this at some point - but I don't think this is a good reason to throw out all the benefits keeping it separate gives you!