X.L.Ant X.L.Ant - 5 months ago 64
Javascript Question

Angular2 Typescript app throws 404 on components when js extension not specified

I just started to play around with Angular2, and ran into a weird component file extension problem:

Let's use the 5 minutes quickstart demo from angular.io (I'll reproduce the code here for reference).

File structure

angular2-quickstart
|- app
| |- app.component.ts
| |- boot.ts
|
|- index.html
|- package.json
|- tsconfig.json


package.json

{
"name": "angular2-quickstart",
"version": "1.0.0",
"scripts": {
"tsc": "tsc",
"tsc:w": "tsc -w",
"lite": "lite-server",
"start": "concurrent \"npm run tsc:w\" \"npm run lite\" "
},
"license": "ISC",
"dependencies": {
"angular2": "2.0.0-beta.0",
"systemjs": "0.19.6",
"es6-promise": "^3.0.2",
"es6-shim": "^0.33.3",
"reflect-metadata": "0.1.2",
"rxjs": "5.0.0-beta.0",
"zone.js": "0.5.10"
},
"devDependencies": {
"concurrently": "^1.0.0",
"lite-server": "^1.3.1",
"typescript": "^1.7.3"
}
}


tsconfig.json

{
"compilerOptions": {
"target": "ES5",
"module": "system",
"moduleResolution": "node",
"sourceMap": true,
"emitDecoratorMetadata": true,
"experimentalDecorators": true,
"removeComments": false,
"noImplicitAny": false
},
"exclude": [
"node_modules"
]
}


app/app.component.ts

import {Component} from 'angular2/core';

@Component({
selector: 'my-app',
template: '<h1>My First Angular 2 App</h1>'
})
export class AppComponent { }


app/boot.ts

import {bootstrap} from 'angular2/platform/browser'
import {AppComponent} from './app.component'

bootstrap(AppComponent);


index.html

<html>

<head>
<title>Angular 2 QuickStart</title>

<!-- 1. Load libraries -->
<script src="node_modules/angular2/bundles/angular2-polyfills.js"></script>
<script src="node_modules/systemjs/dist/system.src.js"></script>
<script src="node_modules/rxjs/bundles/Rx.js"></script>
<script src="node_modules/angular2/bundles/angular2.dev.js"></script>

<!-- 2. Configure SystemJS -->
<script>
System.config({
packages: {
app: {
format: 'register',
defaultExtension: 'js'
}
}
});
System.import('app/boot')
.then(null, console.error.bind(console));
</script>

</head>

<!-- 3. Display the application -->
<body>
<my-app>Loading...</my-app>
</body>

</html>


This works like a charm, but exposes the whole file structure, including
node_modules
and the configuration, which seems like a bad idea.

So I tried to expose only the
app
folder. To achieve that, I did the following:


  • Copy the referenced javascript files in an
    app/scripts
    folder

  • Move the
    index.html
    in
    app

  • Change the references paths in this file

  • Change the
    lite
    script in
    package.json
    to
    lite-server --baseDir app



When running this, everything worked, except that
angular2-polyfills.js
returned :

Error: XHR error (404 Not Found) loading http://localhost:3000/app.component(…)
run @ angular2-polyfills.js:138
zoneBoundFn @ angular2-polyfills.js:111
lib$es6$promise$$internal$$tryCatch @ angular2-polyfills.js:1511
lib$es6$promise$$internal$$invokeCallback @ angular2-polyfills.js:1523
lib$es6$promise$$internal$$publish @ angular2-polyfills.js:1494
lib$es6$promise$$internal$$publishRejection @ angular2-polyfills.js:1444
(anonymous function) @ angular2-polyfills.js:243
run @ angular2-polyfills.js:138zoneBoundFn @ angular2-polyfills.js:111
lib$es6$promise$asap$$flush @ angular2-polyfills.js:1305


Of course, if I ask for
http://localhost:3000/app.component.js
the file is returned correctly.

So my question is: why doesn't the
.js
extension get appended to
app.component
, resulting in this error, where that worked when the server baseDir was the root of the project ? Did I miss some configuration option ?

Answer

You can configure the path to your app folder. In my case, I'm using angular 2 to produce a mobile version of our app and had to configure System like so:

System.config({
            paths: {
                'app/*': './js/mobile/dist/*'
            },
            packages: {        
              app: {
                format: 'register',
                defaultExtension: 'js'
              }
            }
          });
          System.import('app/main')
                .then(null, console.error.bind(console));

As you can see, I decided to map "app" to "dist" where I have my compiled js files to keep them separate from the ts files.

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