How to run SystemJs module when view loads

I have a component that loads a javascript module that builds on Bootstrap.js and Jquery to automatically build a table of contents for a page based on H1,H2,... headers. The component code is as follows:

import { bindable, bindingMode, customElement, noView } from 'aurelia-framework';

@noView()
@customElement('scriptinjector')
export class ScriptInjector {
  @bindable public url;
  @bindable public isLocal;
  @bindable public isAsync;
  @bindable({ defaultBindingMode: bindingMode.oneWay }) protected scripttag;
  private tagId = 'bootTOCscript';

  public attached() {
    if (this.url) {
      this.scripttag = document.createElement('script');
      if (this.isAsync) {
        this.scripttag.async = true;
      }
      if (this.isLocal) {
        System.import(this.url);
        return;
      } else {
        this.scripttag.setAttribute('src', this.url);
      }
      document.body.appendChild(this.scripttag);
    }
  }

  public detached() {
    if (this.scripttag) {
      this.scripttag.remove();
    }
  }
}

Essentially for those not familiar with Aurelia, this simply uses SystemJs to load the bootstrap-toc.js module from my app-bundle wherever I put this on my view:

<scriptinjector url="lib/bootstrap-toc.js" is-local.bind='true'></scriptinjector>

My problem is that although this works perfectly when I first load the view, subsequent visits don't generate a TOC (table of contents). I have checked that Aurelia is in fact calling System.Import each time the view is loaded, but it seems that once a module has been imported once, it is never imported again (the code from the bundle never runs a second time).

Does anyone know how I can unload/reload/reset/rerun the module when I re-enter the view?

Solution

Ok, so after days of fighting with this I have figured out an acceptable solution that keeps all the functionality of the TOC library and requires as few changes to the skeleton project and the target library as I could manage. Forget the script injector above.

In the index.html, do as follows:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Holdings Manager</title>
    <!--The FontAwesome version is locked at 4.6.3 in the package.json file to keep this from breaking.-->
    <link rel="stylesheet" href="jspm_packages/npm/font-awesome@4.6.3/css/font-awesome.min.css">
    <link rel="stylesheet" href="styles/styles.css"> 
    <meta name="viewport" content="width=device-width, initial-scale=1">
  </head>

  <body aurelia-app="main" data-spy="scroll" data-target="#toc">
    <div class="splash">
      <div class="message">Holdings Manager</div>
      <i class="fa fa-spinner fa-spin"></i>
    </div>

    <!-- The bluebird version is locked at 4.6.3 in the package.json file to keep this from breaking -->
    <!-- We include bluebird to bypass Edge's very slow Native Promise implementation. The Edge team -->
    <!-- has fixed the issues with their implementation with these fixes being distributed with the  -->
    <!-- Windows 10 Anniversary Update on 2 August 2016. Once that update has pushed out, you may    -->
    <!-- consider removing bluebird from your project and simply using native promises if you do     -->
    <!-- not need to support Internet Explorer.                                                      -->
    <script src="jspm_packages/system.js"></script>
    <script src="config.js"></script>
    <script src="jspm_packages/npm/bluebird@3.4.1/js/browser/bluebird.min.js"></script>
    <script src="jspm_packages/npm/jquery@2.2.4/dist/jquery.min.js"></script>
    <script src="jspm_packages/github/twbs/bootstrap@3.3.7/js/bootstrap.min.js"></script>
    <script>
      System.import('core-js').then(function() {
        return System.import('polymer/mutationobservers');
      }).then(function() {
        System.import('aurelia-bootstrapper');
      }).then(function() {
        System.import('lib/bootstrap-toc.js');
      });
    </script>

  </body>
</html>

This is assuming you have installed bootstrap using jspm (which brings in jquery as a dependency). This also assumes you have put the javascript library (the one you want to incorporate, bootstrap-toc in my case) in your src/lib folder and that you have configured your bundling to include js files from your source folder.

Next, if your library has a self executing anonymous function defined, you need to take that code and move it inside the 'attached' method of the viewmodel where you want the library to be applied. So in this case, I have a 'help' view with a bunch of sections/subsections that I wanted a TOC generated for, so the code looks like:

import { singleton } from 'aurelia-framework';

@singleton()
export class Help {
  public attached() {
      $('nav[data-toggle="toc"]').each((i, el) => {
        const $nav = $(el);
        window.Toc.init($nav);
      });
  }
}

The code inside the 'attached' method above was cut and pasted from the bootstrap-toc.js file and I removed the self-executing anonymous method.

I tried using system.import for the jquery/bootstrap libraries but that made part of the TOC functionality stop working and I have lost my patience to figure out why so those libraries are staying as script references for now.

Also, when you build the project you will get errors :

help.ts(7,7): error TS2304: Cannot find name '$'.
help.ts(9,16): error TS2339: Property 'Toc' does not exist on type 'Window'.

These do not cause problems at runtime since both $ and Toc will be defined before the view is ever instantiated. You can solve these build errors with this solution here.