Angular 2中的Fetch.js抱怨CORS请求

Question

I'm vaguely following the quickstart tutorial to set up and use angular 2 in an application that communicates with an expressjs backend. I've encounted a few dependency issues and resolved most of them, but I'm stuck. The error I'm encountering is:

Fetch API cannot load npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js. URL scheme must be "http" or "https" for CORS request.

My systemjs.config.js file is verbatim what is specified in their quickstart.

(function(global) {
    System.config({
        paths: {
            'npm': 'node_modules/'
        },

        map: {
            app: 'app',

            // angular bundles
            '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
            '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
            '@angular/compiler': 'npm:@angular/compiler/bundles/compiler.umd.js',
            '@angular/platform-browser': 'npm:@angular/platform-browser/bundles/platform-browser.umd.js',
            '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js',
            '@angular/http': 'npm:@angular/http/bundles/http.umd.js',
            '@angular/router': 'npm:@angular/router/bundles/router.umd.js',
            '@angular/forms': 'npm:@angular/forms/bundles/forms.umd.js',

            // other libraries
            'rxjs':                      'npm:rxjs',
            'angular-in-memory-web-api': 'npm:angular-in-memory-web-api/bundles/in-memory-web-api.umd.js'
        },

        // packages tells the System loader how to load when no filename and/or no extension
        packages: {
            app: {
                defaultExtension: 'js'
            },
            rxjs: {
                defaultExtension: 'js'
            }
        }
    });
})(this);

A lot of the issues I was encountering were resolved by specifying the correct static paths in my expressjs script. What confuses me is why only that file, (platform-browser-dynamic.umd.js) is considered a CORS request. I've confirmed it exists in the directory specified, so that isn't the issue. Does anyone have any insight on this? (most of the clientside source is verbatim from their quickstart for now, if you think it's relevant, just ask and I'll post it).

Answer 1

Troubleshoot for 4 hours, get fed up, post question, find answer moments later.

Twas a typo. Apparently, if you specify a script whose path hasn't been specified and is an otherwise unknown protocol, it will attempt to treat it as a CORS request.

What I had:

path: {
    'npm': 'node_modules/'
}

What it should be:

path: {
    'npm:': 'node_modules/'
}