Forms · Complete runnable example

Select all with mixed state

Represent none, some, or all editable items with one master checkbox.

Try the example Read and copy the source

Live example

This preview runs in an isolated document. Clipboard writes and saved preferences may be blocked, and printing requires the standalone file. A dialog affects only the example. Reset reloads the original example state.

When to use it

Use a master checkbox for a related collection that people may select individually or together. This example excludes the locked item from both the master action and its count.

Try the important details

  1. Inspect the initial mixed state, then select all editable materials.
  2. Uncheck one item and confirm the master becomes indeterminate.
  3. Clear all, verify the locked guide is still checked, then reset to the original selection.

How it works

  • A native fieldset and legend group labeled checkboxes. The master uses the DOM indeterminate property for its mixed state.
  • The script derives eligible items by excluding disabled controls, then recalculates checked and indeterminate after every change.
  • Reset restores defaultChecked values and focuses the master. The live message explicitly counts editable items.

The complete source

The preview, copied text, and downloaded file use this same document.

HTML 

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<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <meta
      http-equiv="Content-Security-Policy"
      content="default-src 'none'; style-src 'unsafe-inline'; script-src 'unsafe-inline'; img-src data: blob:; connect-src 'none'; form-action 'none'; object-src 'none'; base-uri 'none'"
    />
    <title>Make a small collection. | MRHTML example</title>
    <style>
      :root {
        color-scheme: light;
        --ink: #202b36;
        --muted: #596675;
        --line: #d5dde4;
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        gap: 10px;
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      .brand b {
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        letter-spacing: -0.05em;
        font-size: 17px;
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      .brand b span {
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      .brand i {
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      .card {
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        border: 1px solid var(--line);
        border-radius: 18px;
        padding: 32px;
        box-shadow: 0 12px 36px #263a5110;
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      .eyebrow {
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        font-size: 11px;
        font-weight: 700;
        text-transform: uppercase;
        letter-spacing: 0.12em;
        color: var(--blue);
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      h1 {
        font-size: clamp(29px, 5vw, 38px);
        line-height: 1.13;
        letter-spacing: -0.04em;
        margin: 0 0 14px;
      }
      h2 {
        font-size: 20px;
        line-height: 1.3;
        margin: 0 0 14px;
      }
      p {
        margin: 0 0 18px;
      }
      .intro {
        color: var(--muted);
        max-width: 55ch;
      }
      .hint,
      .small {
        font-size: 13px;
        color: var(--muted);
      }
      .hint {
        margin: 9px 0 0;
      }
      .footer {
        font-size: 12px;
        color: var(--muted);
        margin: 20px 2px 0;
      }
      label,
      legend {
        font-weight: 700;
        font-size: 14px;
      }
      label.field {
        display: block;
        margin: 18px 0 7px;
      }
      fieldset {
        min-width: 0;
        margin: 22px 0;
        padding: 20px;
        border: 1px solid var(--line);
        border-radius: 10px;
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      legend {
        padding: 0 7px;
      }
      input,
      select,
      textarea,
      button {
        font: inherit;
      }
      input:not([type='checkbox']):not([type='radio']),
      select,
      textarea {
        width: 100%;
        min-width: 0;
        color: var(--ink);
        background: #fff;
        border: 1px solid #8896a5;
        border-radius: 7px;
        padding: 11px 12px;
        font-size: 16px;
      }
      input[type='checkbox'],
      input[type='radio'] {
        accent-color: var(--blue);
        width: 18px;
        height: 18px;
        flex: none;
      }
      textarea {
        display: block;
        resize: vertical;
      }
      button {
        border: 1px solid var(--blue);
        border-radius: 7px;
        min-height: 44px;
        padding: 10px 17px;
        background: var(--blue);
        color: #fff;
        font-size: 14px;
        font-weight: 700;
        cursor: pointer;
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      button.secondary {
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        color: var(--blue);
      }
      button:disabled {
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      input:disabled,
      select:disabled {
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        color: #596675;
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      :focus-visible {
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      .actions {
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        gap: 10px;
        margin-top: 22px;
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      .status {
        margin: 18px 0 0;
        font-size: 14px;
        min-height: 1.6em;
      }
      .error {
        color: var(--danger);
      }
      .panel {
        background: var(--pale);
        padding: 20px;
        border-radius: 10px;
        margin-top: 24px;
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      .panel p:last-child {
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      .row {
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        gap: 12px;
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      noscript p {
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      code {
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      @media (max-width: 450px) {
        body {
          padding: 25px 14px;
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        .card {
          padding: 23px 19px;
          border-radius: 13px;
        }
        fieldset {
          padding: 16px 13px;
        }
        .brand {
          margin-bottom: 18px;
        }
      }
      @media (prefers-reduced-motion: reduce) {
        *,
        *::before,
        *::after {
          animation: none !important;
          transition: none !important;
          scroll-behavior: auto !important;
        }
      }

      .checklist {
        padding: 0 18px;
      }
      .check-row {
        display: flex;
        align-items: center;
        gap: 14px;
        padding: 16px 0;
        border-bottom: 1px solid var(--line);
        cursor: pointer;
      }
      .check-row:last-child {
        border-bottom: 0;
      }
      .check-row input {
        margin: 0;
      }
      .check-row small {
        display: block;
        font-size: 12px;
        color: var(--muted);
        font-weight: 400;
        margin-top: 3px;
      }
      .master {
        color: var(--blue);
      }
      .unavailable {
        cursor: default;
      }
    </style>
  </head>
  <body>
    <main>
      <p class="brand">
        <b>MR<span>HTML</span></b
        ><span>THE INTERACTION NOTEBOOK</span><i aria-hidden="true"></i>
      </p>
      <section class="card" aria-labelledby="title">
        <p class="eyebrow">05 / Select-all checkboxes</p>
        <h1 id="title">Make a small collection.</h1>
        <p class="intro">
          Choose the reference materials for a fictional project. The master
          checkbox tracks only the three editable items.
        </p>
        <fieldset class="checklist">
          <legend>Reference materials</legend>
          <label class="check-row master"
            ><input id="select-all" type="checkbox" disabled /><span
              >Select all editable items</span
            ></label
          ><label class="check-row"
            ><input type="checkbox" class="item" id="item-notes" checked /><span
              >Field notes<small>A page of observations</small></span
            ></label
          ><label class="check-row"
            ><input type="checkbox" class="item" id="item-colors" /><span
              >Color studies<small>A few promising combinations</small></span
            ></label
          ><label class="check-row"
            ><input type="checkbox" class="item" id="item-sketches" /><span
              >Rough sketches<small>Ideas before details</small></span
            ></label
          ><label class="check-row unavailable"
            ><input
              type="checkbox"
              class="item"
              id="item-guide"
              checked
              disabled
            /><span
              >Project guide<small
                >Included and locked. Excluded from select all.</small
              ></span
            ></label
          >
        </fieldset>
        <p id="selection-count" class="status" role="status" hidden></p>
        <div class="actions">
          <button id="reset-checks" type="button" class="secondary" disabled>
            Reset selection
          </button>
        </div>
        <noscript
          ><p>
            Individual editable checkboxes work without JavaScript. Select all,
            the live count, and reset require JavaScript. The locked guide is
            excluded.
          </p></noscript
        >
      </section>
      <p class="footer">A local MRHTML example. Nothing is sent or saved.</p>
    </main>
    <script>
      (function () {
        'use strict';

        var master = document.getElementById('select-all'),
          items = Array.from(document.querySelectorAll('.item')),
          count = document.getElementById('selection-count'),
          reset = document.getElementById('reset-checks');
        function eligible() {
          return items.filter(function (item) {
            return !item.disabled;
          });
        }
        function update() {
          var editable = eligible(),
            checked = editable.filter(function (item) {
              return item.checked;
            }).length;
          master.checked = editable.length > 0 && checked === editable.length;
          master.indeterminate = checked > 0 && checked < editable.length;
          master.disabled = editable.length === 0;
          count.textContent =
            checked +
            ' of ' +
            editable.length +
            ' editable items selected. Locked items are unchanged.';
        }
        master.addEventListener('change', function () {
          eligible().forEach(function (item) {
            item.checked = master.checked;
          });
          update();
        });
        items.forEach(function (item) {
          item.addEventListener('change', update);
        });
        reset.addEventListener('click', function () {
          items.forEach(function (item) {
            item.checked = item.defaultChecked;
          });
          update();
          master.focus();
        });
        count.hidden = false;
        reset.disabled = false;
        update();
      })();
    </script>
  </body>
</html>