How to import a npm package in an angular2 component?
I'm trying to learn the ropes of ng2 and the depedency injection system is killing me.
I'm using the ng quickstart from: https://github.com/angular/quickstart/blob/master/README.md
I'm trying to import this package into the app: https://www.npmjs.com/package/arpad. I installed the package via npm update, my package.json dependencies look like this:
"dependencies": {
"angular2": "2.0.0-beta.9",
"systemjs": "0.19.24",
"es6-promise": "^3.0.2",
"es6-shim": "^0.35.0",
"reflect-metadata": "0.1.2",
"rxjs": "5.0.0-beta.2",
"zone.js": "0.5.15",
"arpad":"^0.1.2" <----- the package i'm trying to import
}
This is how the package exports its code:
module.exports = ELO;
I have a component importing the module like this:
import {ELO} from 'node_modules/arpad/index.js';
This is how systemJS is configured in the application's index.html:
<script>
System.config({
packages: {
app: {
format: 'register',
defaultExtension: 'js'
}
},
map:{'arpad':'node_modules/arpad'} <---- here
});
System.import('node_modules/arpad/index.js'); <--- and here for good measure
System.import('app/main')
.then(null, console.error.bind(console));
</script>
Now, it looks a lot like I'm shooting in the dark, and that's exactly what the error messages in the application console had me doing. When I try to use the module in the component like this:
public elo = ELO;
constructor(){
this.score = this.elo.expectedScore(200, 1000);
---- there is more to the component but this is the part where it breaks
}
I get the following message:
"ORIGINAL EXCEPTION: TypeError: this.elo is undefined"
So the question in a broader scope is:
How can I get a given npm package (that is not already an angular module) to work in a component or service using systemJS(or Webpack, or Browserify) as module loader in the ng2 quickstart?
I have some comments here:
You should configure SystemJS this way for your module:
System.config({
map:{'arpad':'node_modules/arpad/index.js'}
packages: {
app: {
format: 'register',
defaultExtension: 'js'
}
}
});
You don't need to import your index.js file (see System.import('node_modules/arpad/index.js'); ) before importing your application (importing the app/main module).
You need to import your elo object this way:
import * as Elo from 'arpad';
Then you should be able to use your module this way:
constructor() {
this.elo = new Elo();
this.score = this.elo.expectedScore(200, 1000);
}
Here is a plunkr describing this: https://plnkr.co/edit/K6bx97igIHpcPZqjQkkb?p=preview.
链接地址: http://www.djcxy.com/p/90772.html