The StaticSearch class should emit custom events

[martindholmes]

There's a common requirement to be able to do some post-processing or enhancements whenever specific things happen with the instantiated StaticSearch class; examples are:

• When the Sch object has been fully instantiated, add something to it
• When a search has been initiated, show some interface signal
• When a search has been completed, do something
• When the search results have been rendered onto the page, do something

This would be made much easier if StaticSearch emitted custom events which other code could listen for. Here's an example (untested, off the top of my head, but something I'd like to be able to do in a current project):

//at the end of StaticSearch~processResults: existing code:
      this.isSearching = false;
      this.searchFinishedHook(4);
//new code
      const evt = new CustomEvent('ssResultsRendered', {detail: { 'hits': this.resultSet.getSize()} });
      window.dispatchEvent(evt);

//existing code
      return (this.resultSet.getSize() > 0);

And this could be hooked by the site-specific code:

window.addEventListener('ssResultsRendered', function(evt){console.log(evt.detail.hits + ' results were rendered on the page.');});

(I would use this particular case to insert a special link enabling the searcher to view all the results rendered together in a single page, if the number of results is sufficiently small for this to be manageable.)

[martindholmes]

Working on this in issue-331-events branch. Custom events so far:

• ssInstantiated: dispatched at the end of the object constructor.
• ssJsonRetrieved: dispatched when the initial collection of Json files has been retrieved.
• ssSearchStarting: dispatched before starting a search.
• ssFormCleared: dispatched after clearing the search form controls.
• ssSearchCompleted: dispatched after results are rendered (or the warning message appears for too many results).

[martindholmes]

The events above are now added and working (confirmed by adding a small block of code to the test suite JS).

[martindholmes]

What's required now is some documentation, but that will have to wait until the documentation CSS work is finished and merged.

[martindholmes]

PR is merged; documentation still to do, so keeping this open as a reminder.