Angular2 / DatePipe for Japanese

<!DOCTYPE html>
<html>

  <head>
    <base href="." />
    <title>angular2 playground</title>
    <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script>
    <script src="https://unpkg.com/zone.js/dist/zone.js"></script>
    <script src="https://unpkg.com/zone.js/dist/long-stack-trace-zone.js"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script>
    <script src="https://unpkg.com/systemjs@0.19.31/dist/system.js"></script>
    <script src="config.js"></script>
    <script>
    System.import('app')
      .catch(console.error.bind(console));
  </script>
  </head>

  <body>
    <my-app>
    loading...
  </my-app>
  </body>

</html>

/* Styles go here */

System.config({
  //use typescript for compilation
  transpiler: 'typescript',
  //typescript compiler options
  typescriptOptions: {
    emitDecoratorMetadata: true
  },
  paths: {
    'npm:': 'https://unpkg.com/'
  },
  //map tells the System loader where to look for things
  map: {
    
    'app': './src',
    
    '@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',
    
    '@angular/core/testing': 'npm:@angular/core/bundles/core-testing.umd.js',
    '@angular/common/testing': 'npm:@angular/common/bundles/common-testing.umd.js',
    '@angular/compiler/testing': 'npm:@angular/compiler/bundles/compiler-testing.umd.js',
    '@angular/platform-browser/testing': 'npm:@angular/platform-browser/bundles/platform-browser-testing.umd.js',
    '@angular/platform-browser-dynamic/testing': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic-testing.umd.js',
    '@angular/http/testing': 'npm:@angular/http/bundles/http-testing.umd.js',
    '@angular/router/testing': 'npm:@angular/router/bundles/router-testing.umd.js',
    
    'rxjs': 'npm:rxjs',
    'typescript': 'npm:typescript@2.0.2/lib/typescript.js'
  },
  //packages defines our app package
  packages: {
    app: {
      main: './main.ts',
      defaultExtension: 'ts'
    },
    rxjs: {
      defaultExtension: 'js'
    }
  }
});

//main entry point
import {platformBrowserDynamic} from '@angular/platform-browser-dynamic';
import {AppModule} from './app';

platformBrowserDynamic().bootstrapModule(AppModule)

//our root app component
import {Component, NgModule} from '@angular/core';
import {DatePipe} from '@angular/common';
import {BrowserModule} from '@angular/platform-browser';

// pipe
import {DateJpPipe} from './date-jp.pipe';

@Component({
  selector: 'my-app',
  template: `
  <div>
    DatePipe('en-US'):   {{ today | date: 'y/MM/dd (EEE) HH:mm' }}
  </div>
  <div>
    DatePipe('ja-JP'):   {{ ngDatePipeJp.transform(today, 'yMMdd (EEE) HHmm') }}
  </div>
  <div>
    dateJP(lite):   {{ today | dateJP: 'y/MM/dd (EEE) HH:mm' }}
  </div>
  `
})

export class App {
  today = new Date();
  ngDatePipeJp = new DatePipe('ja-JP');
}

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ App, DateJpPipe ],
  bootstrap: [ App ]
})
export class AppModule {}

import { Pipe } from '@angular/core';
import { DatePipe } from '@angular/common';

@Pipe({name: 'dateJP'})
export class DateJpPipe {
  private dateJpPipe: DatePipe;

  constructor() {
    this.dateJpPipe = new DatePipe('en-US');
  }

  transform(date, format) {
    const week = {
      'Mon': '月',
      'Tue': '火',
      'Wed': '水',
      'Thu': '木',
      'Fri': '金',
      'Sat': '土',
      'Sun': '日'
    };

    // dateが空だったら抜ける
    if (!date) return;

    let dateFormat = this.dateJpPipe.transform(date, format);
    dateFormat.match(/([a-z]+)/i).map((val, index) => {
      if (index === 0) return; // 最初の要素は使わないので抜ける
      dateFormat = dateFormat.replace(new RegExp(val, 'i'), week[val]);
    });
    return dateFormat;
  }
}