How to manage DOM element dependencies

Question

I am trying to create a web-page where some elements (forms and buttons) become visible or are being hidden when some other elements (buttons) are clicked.
I try to find a way to manage this, that is re-usable, and easy to maintain.

My current solution is shown below, but I hope someone has a more elegant solution.
The problem with my own solution is that it will become difficult to read when the number of dependencies increase. It will then also require a lot of editing when I add another button and form.

---

My current solution is to use an observable to manage the state of the forms, like this:

HTML:

  <button id="button-A">Show form A, hide button A and B</button>
  <button id="button-B">Show form B, hide button A and B</button>
  <form id="form-A">
    ...this form is initially hidden
    ...some form elements
    <button id="cancel-A">Hide form A, show button A and B</button>
  </form>
  <form id="form-B">
    ...this form is initially hidden
    ...some form elements
    <button id="cancel-B">Hide form B, show button A and B</button>
  </form>

Dart:

  import 'dart:html';
  import 'package:observe/observe.dart';

  final $ = querySelector;
  final $$ = querySelectorAll;

  Map<String, bool> toBeObserved = {
    "showFormA" : false,
    "showFormB" : false
  };

  // make an observable map
  ObservableMap observeThis = toObservable(toBeObserved);

  // start managing dependencies
  main() {
    // add click event to buttons
    $('#button-A')
    ..onClick.listen((E) => observeThis["showFormA"] = true);
    $('#button-B')
    ..onClick.listen((E) => observeThis["showFormB"] = true);

    // add click events to form buttons
    $('#cancel-A')
    ..onClick.listen((E) {
      E.preventDefault();
      E.stopPropagation();
      observeThis["showFormA"] = false;
    });
    $('#cancel-B')
    ..onClick.listen((E) {
      E.preventDefault();
      E.stopPropagation();
      observeThis["showFormB"] = false;
    });

    // listen for changes
    observeThis.changes.listen((L) {

      L.where((E) => E.key == 'showFormA').forEach((R) {
        $('#form-A').style.display = (R.newValue) ? 'block' : 'none';
        $('#button-A').style.display = (R.newValue || observeThis['showFormB']) ? 'none' : 'inline-block';
        $('#button-B').style.display = (R.newValue || observeThis['showFormB']) ? 'none' : 'inline-block';
      });
      L.where((E) => E.key == 'showFormB').forEach((R) {
        $('#form-B').style.display = (R.newValue) ? 'block' : 'none';
        $('#button-A').style.display = (R.newValue || observeThis['showFormA']) ? 'none' : 'inline-block';
        $('#button-B').style.display = (R.newValue || observeThis['showFormA']) ? 'none' : 'inline-block';
      });

    });
  }

Answer 1

You could use polymer's template functionality like

<template if="showA">...

This should work without embedding your elements within Polymer elements too.
This discussion provides some information how to use <template> without Polymer elements. Using Polymer elements could also be useful.
It all depends on your requirements/preferences.

Angular.dart is also useful for such view manipulation.

If you want to use plain Dart/HMTL I don't have ideas how to simplify your code.

Answer 2

You can use basic CSS to show/hide the elements.

HTML

<div id="container" class="show-buttons">
    <button id="button-A" class="btn" data-group="a">...</button>
    <button id="button-B" class="btn" data-group="b">...</button>
    <form id="form-A" class="form group-a">...</button>
    <form id="form-B" class="form group-b">...</button>
</div>

CSS

.btn, .form {
  display: none;
}

.show-buttons .btn,
.show-a .form.group-a,
.show-b .form.group-b {
  display: block;
}

In Dart just get the data-group (or whatever you want to call this) attribute from the button. Toggle the CSS classes (show-buttons, show-a and show-b) on the container element to switch between the buttons and the specific forms.

This solution is very easy to extend on.

Answer 3

You can use something like this to handle all the elements in a generic way :

final Iterable<ButtonElement> buttons = querySelectorAll('button')
    .where((ButtonElement b) => b.id.startsWith('button-'));

final Iterable<ButtonElement> cancels = querySelectorAll('button')
    .where((ButtonElement b) => b.id.startsWith('cancel-'));

final Iterable<FormElement> forms = querySelectorAll('form')
    .where((FormElement b) => b.id.startsWith('form-'));

buttons.forEach((b) {
  b.onClick.listen((e) {
    // name of clicked button
    final name = b.id.substring(b.id.indexOf('-') + 1);
    // hide all buttons
    buttons.forEach((b) => b.hidden = true)
    // show the good form
    querySelector('#form-$name').hidden = false;
  });
});

cancels.forEach((b) {
  b.onClick.listen((e) {
    // show all buttons
    buttons.forEach((b) => b.hidden = false);
    // hide all forms
    forms.forEach((b) => b.hidden = true);
    // prevent default
    e.preventDefault();
  });
});

// hide all form at startup
forms.forEach((f) => f.hidden = true);