title: How to write Helper class in typescript?
body: <p>I have a problem when use <code>typeScript</code> with <code>angular2</code>.<br>
  I want create one <code>helper.ts</code> file exports many classed/functions common to re-use.<br>
  But <code>Helper class</code> need import others service in constructor, so that when another class import <code>Helper class</code>, It have to set param is those service. I don't want this. </p>
  
  <p>How I can write <code>Helper class</code>, that I can use anywhere when <code>import {Helper} from ..</code> </p>
  
  <p>This is my sample:
  Helper.ts</p>
  
  <pre><code>import {TranslateService, TranslatePipe} from 'ng2-translate/ng2-translate';
  import {Inject, Component} from 'angular2/core';
  
  
  @Component({
      providers: [TranslateService]
  })
  
  export class Helpper {
      public trans;
      public lang;
      public properties;
  
      constructor(trans: TranslateService) {
          this.trans = trans;
          //This is variable for translate function 
          this.lang = this.trans.currentLang;
          this.properties = this.trans.translations[this.lang];             
      }
  
      translate(key) {
          return this.properties[key];      
      }      
  }
  </code></pre>
  
  <p>RenderTab.ts</p>
  
  <pre><code>import {Component, Inject, Injectable} from 'angular2/core';
  import {Helper} from './helpper'
  
  @Component({
      providers: [Helper]
  })
  
  export class RenderTab {
      public helper;
  
      constructor(helper: Helper) { 
          this.helper = helper;
      }
  
      render() {
          var test = this.helper.translate('string');
      }
  }
  </code></pre>
  
  <p>HomePage.ts</p>
  
  <pre><code>import {Component, Inject, Injectable} from 'angular2/core';
  import {RenderTab} from './RenderTab'
  
  @Component({
      selector: 'div',
      templateUrl: './HomePage.html',
      providers: [RenderTab]
  })
  
  export class ColorPicker {
      public renderTab;
  
      constructor(renderTab: RenderTab) { 
          this.renderTab = renderTab;
  
          var test = this.renderTab.render();
      }
  }
  </code></pre>
  
  <p>Please help me, thanks.</p>