| 1 | // Makes the server-rendered TodoMVC behave like the reference app. |
| 2 | // |
| 3 | // Every change is still the form POST the page uses with JavaScript off. |
| 4 | // This module sends that same POST in the background with an |
| 5 | // X-Todo-Fragment header, and the server answers with fresh HTML for the |
| 6 | // list and footer instead of a redirect. The server stays the only place |
| 7 | // that decides what the page shows. |
| 8 | |
| 9 | const app = document.querySelector('.todoapp'); |
| 10 | const newTodo = app.querySelector('.new-todo'); |
| 11 | |
| 12 | // Requests run one at a time, so their answers land in the order they |
| 13 | // were made. |
| 14 | let queue = Promise.resolve(); |
| 15 | let swapping = false; |
| 16 | |
| 17 | function send(form) { |
| 18 | const body = new URLSearchParams(new FormData(form)); |
| 19 | const url = form.action; |
| 20 | queue = queue |
| 21 | .then(async () => { |
| 22 | const res = await fetch(url, { |
| 23 | method: 'POST', |
| 24 | body, |
| 25 | headers: { 'X-Todo-Fragment': '1' }, |
| 26 | }); |
| 27 | if (!res.ok) throw new Error(`${res.status} from ${url}`); |
| 28 | swap(await res.text()); |
| 29 | }) |
| 30 | .catch((err) => { |
| 31 | // Something is out of step (an expired list, a lost connection). |
| 32 | // The server's page is the truth, so load it. |
| 33 | console.error(err); |
| 34 | location.reload(); |
| 35 | }); |
| 36 | } |
| 37 | |
| 38 | // Replaces section.main and footer.footer with the server's HTML, keeping |
| 39 | // keyboard focus on the same control where it still exists, and keeping |
| 40 | // any edit still in progress (one not yet being saved) open with its |
| 41 | // draft intact. |
| 42 | function swap(html) { |
| 43 | const again = focusSelector(document.activeElement); |
| 44 | const drafts = [...app.querySelectorAll('.todo-list li.editing:not([data-saving])')].map((li) => { |
| 45 | const input = li.querySelector('.edit'); |
| 46 | return { |
| 47 | id: li.dataset.id, |
| 48 | value: input.value, |
| 49 | focused: input === document.activeElement, |
| 50 | start: input.selectionStart, |
| 51 | end: input.selectionEnd, |
| 52 | }; |
| 53 | }); |
| 54 | // Removing a focused field can fire focusout; that isn't the visitor |
| 55 | // leaving the field, so it mustn't save. |
| 56 | swapping = true; |
| 57 | for (const el of app.querySelectorAll(':scope > .main, :scope > .footer')) el.remove(); |
| 58 | swapping = false; |
| 59 | const t = document.createElement('template'); |
| 60 | t.innerHTML = html; |
| 61 | app.append(t.content); |
| 62 | for (const d of drafts) { |
| 63 | const li = app.querySelector(`.todo-list li[data-id="${CSS.escape(d.id)}"]`); |
| 64 | if (!li) continue; // the item is gone, so is its edit |
| 65 | const input = li.querySelector('.edit'); |
| 66 | li.classList.add('editing'); |
| 67 | input.value = d.value; |
| 68 | if (d.focused) { |
| 69 | input.focus(); |
| 70 | input.setSelectionRange(d.start, d.end); |
| 71 | } |
| 72 | } |
| 73 | if (again && !drafts.some((d) => d.focused)) app.querySelector(again)?.focus(); |
| 74 | } |
| 75 | |
| 76 | function focusSelector(el) { |
| 77 | if (!el || !app.contains(el) || el === newTodo) return null; |
| 78 | if (el.id) return `#${CSS.escape(el.id)}`; |
| 79 | const li = el.closest('li[data-id]'); |
| 80 | if (li && el.classList.length) { |
| 81 | return `li[data-id="${CSS.escape(li.dataset.id)}"] .${CSS.escape(el.classList[0])}`; |
| 82 | } |
| 83 | return null; |
| 84 | } |
| 85 | |
| 86 | // Adding, deleting, clearing completed, and saving an edit with Enter all |
| 87 | // arrive here as ordinary form submissions. |
| 88 | app.addEventListener('submit', (e) => { |
| 89 | const form = e.target; |
| 90 | e.preventDefault(); |
| 91 | const edit = form.querySelector('.edit'); |
| 92 | if (edit) { |
| 93 | saveEdit(edit); |
| 94 | return; |
| 95 | } |
| 96 | send(form); |
| 97 | if (form.contains(newTodo)) newTodo.value = ''; |
| 98 | }); |
| 99 | |
| 100 | // The checkboxes have no submit button of their own: a change submits the |
| 101 | // form they sit in. |
| 102 | app.addEventListener('change', (e) => { |
| 103 | if (e.target.matches('.toggle, .toggle-all')) send(e.target.form); |
| 104 | }); |
| 105 | |
| 106 | // Double-click a title to edit it. |
| 107 | app.addEventListener('dblclick', (e) => { |
| 108 | const label = e.target.closest('.todo-list label'); |
| 109 | if (!label) return; |
| 110 | const li = label.closest('li'); |
| 111 | const input = li.querySelector('.edit'); |
| 112 | li.classList.add('editing'); |
| 113 | input.focus(); |
| 114 | input.setSelectionRange(input.value.length, input.value.length); |
| 115 | }); |
| 116 | |
| 117 | // Escape cancels the edit; leaving the field saves it. |
| 118 | app.addEventListener('keydown', (e) => { |
| 119 | if (e.key !== 'Escape' || !e.target.matches('.edit')) return; |
| 120 | const input = e.target; |
| 121 | input.value = input.defaultValue; |
| 122 | input.closest('li').classList.remove('editing'); |
| 123 | }); |
| 124 | |
| 125 | app.addEventListener('focusout', (e) => { |
| 126 | if (!swapping && e.target.matches('.edit')) saveEdit(e.target); |
| 127 | }); |
| 128 | |
| 129 | // Saves an edit once, however many ways it was finished (Enter, then the |
| 130 | // blur that follows when the item is redrawn). |
| 131 | function saveEdit(input) { |
| 132 | const li = input.closest('li'); |
| 133 | if (!li.classList.contains('editing') || li.dataset.saving) return; |
| 134 | li.dataset.saving = '1'; |
| 135 | if (input.value.trim() === input.defaultValue) { |
| 136 | // Unchanged: nothing to send, just leave edit mode. |
| 137 | input.value = input.defaultValue; |
| 138 | li.classList.remove('editing'); |
| 139 | delete li.dataset.saving; |
| 140 | return; |
| 141 | } |
| 142 | send(input.form); |
| 143 | } |
| 144 | |
amadan