Using Modules in the Browser (without WebPack)

问题

I'm grokking my way through ES6 and I ran into Modules (nice!) and in learning, I am trying to see if I can use them in the browser without WebPack (which I haven't learned yet).

So, I have the following files/folder structure in my JS directory

js

 - lib (for complied es6 via Babel)
   - mods (compiled modules)
     - module.js (compiled via Babel)
   - app.js (imports modules, attached to index.html)

 - src (for "raw" es6)
   - mods (es6 modules)
     - module.js (es6 module)
   - app.js (imports modules)

In js/src/mods/module.js, I have the following code....

export const topTime = 1.5;

export const subTime = 0.75;

Which is imported by js/src/app.js ...

import { topTime, subTime } from './mods/modules';

console.log(topTime);

console.log(subTime);

I then compiled all es6 files to es5 (which placed the files in the lib dir.)
```
npm run babel
```
Now I can run the main file (js/lib/app.js) inside my editor (vscode/output tab)
```
[Running] node "/home/me/www/es6.local/js/lib/app.js"

1.5

0.75
```

...but I think that is only because it's running in node.

It breaks when I call my index.html file (with js/lib/app.js) in the browser (FF) as I get the following error...
```
ReferenceError: require is not defined
```

So I see that babel compiled this...

import { topTime, subTime } from './mods/modules';

into this...

var _modules = require('./mods/modules');

...But I thought this was valid es5? ...no? So HOW was this done BEFORE webpack? Please advise.

Here is my package.json (in case it helps)...

{
  "name": "es6.local",
  "version": "0.0.1",
  "description": "JavaScript ES6 Testing Sandbox",
  "main": "index.html",
  "scripts": {
    "babel": "babel js/src --out-dir js/lib --source-maps"
  },
  "author": "Student",
  "license": "ISC",
  "devDependencies": {
    "eslint": "^4.16.0",
    "eslint-plugin-import": "^2.8.0",
    "eslint-plugin-jsx-a11y": "^6.0.3",
    "eslint-plugin-react": "^7.6.0",
    "eslint-config-airbnb": "^16.1.0",
    "babel-cli": "^6.26.0",
    "babel-polyfill": "^6.26.0",
    "babel-preset-env": "^1.6.1"
  },
  "babel": {
    "presets": [
      [
        "env",
        {
          "targets": {
            "browsers": [
              "last 2 versions",
              "safari >= 7"
            ]
          }
        }
      ]
    ]
  }
}

回答1:

It's a pain.

exports and require are part of the CommonJS spec. If I remember correctly, webpack implements it internally. You need the same functionality, because it's not part of ES5.

Try RequireJS, or something similar to load your modules.

回答2:

I've been stuck with this for a while and after playing around I found a solution. You don't need any libraries or webpack to do this and I'm not sure this works outside of chrome.

You need to run this code on a webserver or else it won't work (in other words, it has to be on localhost, NOT file://)
Make a folder called jsmodule
create a file called index.html with the following code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Js module</title>
</head>
<body>
    <h1>JS module test</h1>
    <script type="module" src="script.js"></script>
</body>
</html>

Create a file in same folder called script.js with the following code:

import Person from './Person.js';
import Book from './Book.js';


let person1 = new Person();
let someBook = new Book();

create a file in same folder called Person.js with the following code:

export default class Person{
    constructor(){
        alert("hallo from person");
    }
}

create a file in same folder called Book.js with the following code:

export default class Book{
    constructor(){
        alert("Hallo from book");
    }
}

Run the index.html on you webserver (localhost)

来源：https://stackoverflow.com/questions/48492736/using-modules-in-the-browser-without-webpack

标签

javascript

Webpack

ecmascript-6

babeljs

ecmascript-5