Checkbox (Single)

Whenever possible, you should use native HTML checkboxes, but it is possible to create ARIA checkboxes that act exactly like native checkboxes, for both sighted users and screen reader users, as this pattern shows.



Choose World Peace

Initial HTML Markup

<p>
  <span class="deque-checkbox-aria" aria-labelledby="worldpeace"></span>
  <span id="worldpeace">Choose World Peace</span>
</p>

JavaScript

Required: The complete JavaScript file (for all patterns in the library): deque-patterns.min.js

Key parts of the JavaScript file

Note: The code below is functional only in the context of the complete JavaScript file.

In the @checkbox section:


	function toggle(element) {
	  if (isToggledOn(element)) {
	    toggleOff(element);
	  } else {
	    toggleOn(element);
	  }
	} /*
	  
	  TO DO:
	  
	  - Throw an error if the label is missing
	  */
	
	function isToggledOn(element) {
	  return getCheckboxData(element) === 'true';
	}
	
	function setCheckboxData(element, value) {
	  element.setAttribute('aria-checked', value);
	  var dataElement = document.getElementById('checkboxTristateData[' + element.getAttribute('aria-labelledby') + ']');
	  if (dataElement) dataElement.value = value;
	}
	
	function getCheckboxData(element) {
	  var dataElement = document.getElementById('checkboxTristateData[' + element.getAttribute('aria-labelledby') + ']');
	  return dataElement ? dataElement.value : null;
	}
	
	function toggleOn(element) {
	  setCheckboxData(element, 'true');
	}
	
	function toggleOff(element) {
	  setCheckboxData(element, 'false');
	}
	
	function toggleMixed(element) {
	  setCheckboxData(element, 'mixed');
	}
	function createSingleCheckbox(checkbox, isChecked) {
	  var onChange = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : function () {};
	
	
	  checkbox.setAttribute('tabindex', '0');
	  checkbox.setAttribute('role', 'checkbox');
	
	  var indicator = document.createElement('span');
	  indicator.classList.add('deque-checkbox-indicator');
	
	  checkbox.appendChild(indicator);
	
	  var labelText = checkbox.getAttribute('aria-labelledby');
	  var label = document.getElementById(labelText);
	  label.setAttribute('aria-hidden', 'true'); // prevents double readout
	  label.classList.add('deque-checkbox-label');
	
	  var hiddenCheckbox = document.createElement('input');
	  hiddenCheckbox.type = 'hidden';
	  hiddenCheckbox.name = 'checkboxTristateData[' + labelText + ']';
	  hiddenCheckbox.id = 'checkboxTristateData[' + labelText + ']';
	  hiddenCheckbox.classList.add('deque-checkbox-data');
	
	  checkbox.appendChild(hiddenCheckbox);
	
	  if (isChecked) {
	    toggleOn(checkbox);
	  } else {
	    toggleOff(checkbox);
	  }
	
	  function changeHandler(e) {
	    e.stopPropagation();
	    e.preventDefault();
	    toggle(checkbox);
	    broadcastChange();
	  }
	
	  function broadcastChange() {
	    onChange({ element: checkbox, isToggledOn: isToggledOn(label) });
	  }
	
	  checkbox.parentNode.addEventListener('click', changeHandler);
	  (0, _keyboardUtils.onElementSpace)(checkbox, changeHandler);
	
	  checkbox.parentNode.addEventListener('focus', function () {
	    checkbox.classList.add('deque-checkbox-focused');
	  });
	
	  checkbox.parentNode.addEventListener('blur', function () {
	    checkbox.classList.remove('deque-checkbox-focused');
	  });
	
	  return checkbox;
	}
	
	function createSingleCheckboxForRadio(checkbox, checkboxLabel, isChecked) {
	  var onChange = arguments.length > 3 && arguments[3] !== undefined ? arguments[3] : function () {};
	
	
	  checkbox.setAttribute('tabindex', '0');
	  checkbox.setAttribute('role', 'checkbox');
	
	  var indicator = document.createElement('span');
	  indicator.classList.add('deque-checkbox-indicator');
	
	  checkbox.appendChild(indicator);
	
	  var labelText = checkbox.getAttribute('aria-labelledby');
	  var label = document.getElementById(labelText);
	  label.setAttribute('aria-hidden', 'true'); // prevents double readout
	  label.classList.add('deque-checkbox-label');
	
	  var hiddenRadio = document.createElement('input');
	  hiddenRadio.type = 'hidden';
	  hiddenRadio.name = 'checkboxTristateData[' + labelText + ']';
	  hiddenRadio.id = 'checkboxTristateData[' + labelText + ']';
	  hiddenRadio.classList.add('deque-checkbox-radio-data');
	  checkbox.appendChild(hiddenRadio);
	
	  if (isChecked) {
	    toggleOn(checkbox);
	  } else {
	    toggleOff(checkbox);
	  }
	
	  function changeHandler(e) {
	    e.stopPropagation();
	    e.preventDefault();
	    toggle(checkbox);
	    broadcastChange();
	  }
	
	  function broadcastChange() {
	    onChange({ element: checkbox, isToggledOn: isToggledOn(label) });
	  }
	
	  checkbox.addEventListener('click', changeHandler);
	  checkboxLabel.addEventListener('click', changeHandler);
	  (0, _keyboardUtils.onElementSpace)(checkbox, changeHandler);
	
	  checkbox.addEventListener('focus', function () {
	    checkbox.classList.add('deque-radio-focused');
	  });
	
	  checkbox.addEventListener('blur', function () {
	    checkbox.classList.remove('deque-radio-focused');
	  });
	
	  return checkbox;
	}
	
	function createCheckboxGroup(parent, children) {
	  var onChange = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : function () {};
	
	
	  parent = createSingleCheckbox(parent, false, function (e) {
	    onChange(e);
	    rootClicked(getCorrectRootState());
	  });
	
	  children = Array.prototype.slice.call(children);
	
	  children = children.map(function (child) {
	    return createSingleCheckbox(child, false, function () {
	      if (onChange) {
	        onChange(child);
	      }
	      setCorrectRootState();
	    });
	  });
	
	  var rootClickHandlers = {
	    'true': function _true() {
	      children.forEach(toggleOff);
	      toggleOff(parent);
	    },
	    'false': function _false() {
	      children.forEach(toggleOn);
	      toggleOn(parent);
	    },
	    'mixed': function mixed() {
	      children.forEach(toggleOn);
	      toggleOn(parent);
	    }
	  };
	
	  function rootClicked(rootState) {
	    rootClickHandlers[rootState]();
	  }
	
	  function getCorrectRootState() {
	    if (children.every(isToggledOn)) {
	      return 'true';
	    } else if (children.every(function (child) {
	      return !isToggledOn(child);
	    })) {
	      return 'false';
	    } else {
	      return 'mixed';
	    }
	  }
	
	  var leafClickHandlers = {
	    'true': function _true() {
	      return toggleOn(parent);
	    },
	    'false': function _false() {
	      return toggleOff(parent);
	    },
	    'mixed': function mixed() {
	      return toggleMixed(parent);
	    }
	  };
	
	  function setCorrectRootState() {
	    leafClickHandlers[getCorrectRootState()]();
	  }
	}
	
	function activateAllCheckboxes() {
	  var checkboxes = document.querySelectorAll('.deque-checkbox-aria');
	  for (var i = 0; i < checkboxes.length; i++) {
	    createSingleCheckbox(checkboxes[i], false);
	  }
	
	  var tristates = document.querySelectorAll('.deque-checkbox-tristate-group');
	  for (var j = 0; j < tristates.length; j++) {
	    var parentGroup = tristates[j].querySelector('.deque-checkbox-tristate-parent');
	    var parent = parentGroup.querySelector('.deque-checkbox-tristate');
	    var childrenGroup = tristates[j].querySelector('.deque-checkbox-tristate-children');
	    var children = childrenGroup.querySelectorAll('.deque-checkbox-tristate');
	    createCheckboxGroup(parent, children);
	  }
	}
	
	activateAllCheckboxes();
	
	

In the @keyboardUtils section:


	var KEYS = exports.KEYS = {
	  BACKSPACE: 8,
	  TAB: 9,
	  ENTER: 13,
	  SHIFT: 16,
	  CTRL: 17,
	  ALT: 18,
	  ESCAPE: 27,
	  SPACE: 32,
	  LEFT: 37,
	  RIGHT: 39,
	  UP: 38,
	  DOWN: 40,
	  F10: 121,
	  HOME: 36,
	  END: 35,
	  PAGE_UP: 33,
	  PAGE_DOWN: 34
	};
	
	function bindElementToEventValue(element, eventName, testValue, handler) {
	  function localHandler(e) {
	    if (e.which === testValue) {
	      handler(e);
	    }
	  }
	
	  element.addEventListener(eventName, localHandler);
	  return function () {
	    element.removeEventListener(eventName, localHandler);
	  };
	}
	
	function bindElementToKeypressValue(element, testValue, handler) {
	  return bindElementToEventValue(element, 'keypress', testValue, handler);
	}
	
	function bindElementToKeydownValue(element, testValue, handler) {
	  return bindElementToEventValue(element, 'keydown', testValue, handler);
	}
	
	function onElementEnter(element, handler) {
	  return bindElementToKeypressValue(element, KEYS.ENTER, handler);
	}
	
	function onElementEscape(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.ESCAPE, handler);
	}
	
	function onElementSpace(element, handler) {
	  return bindElementToKeypressValue(element, KEYS.SPACE, handler);
	}
	
	function onElementLeft(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.LEFT, handler);
	}
	
	function onElementRight(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.RIGHT, handler);
	}
	
	function onElementUp(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.UP, handler);
	}
	
	function onElementDown(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.DOWN, handler);
	}
	
	function onElementHome(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.HOME, handler);
	}
	
	function onElementEnd(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.END, handler);
	}
	
	function onElementPageUp(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.PAGE_UP, handler);
	}
	
	function onElementPageDown(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.PAGE_DOWN, handler);
	}
	
	function onElementF10(element, handler) {
	  return bindElementToKeydownValue(element, KEYS.F10, handler);
	}
	
	function isAlphaNumeric(charCode) {
	  return charCode >= 48 && charCode <= 90 /* numbers, uppercase letters */
	  || charCode >= 97 && charCode <= 122 /* lowercase letters */;
	}
	
	function onElementCharacter(element, handler) {
	  function localHandler(e) {
	    var charCode = e.which;
	    if (isAlphaNumeric(charCode)) {
	      handler(e);
	    }
	  }
	
	  element.addEventListener('keypress', localHandler);
	  return function () {
	    element.removeEventListener('keypress', localHandler);
	  };
	}
	
	function trapEnter(element) {
	  onElementEnter(element, function (e) {
	    e.stopPropagation();
	    e.preventDefault();
	  });
	}
	

In the @guidUtils section:


	/*
	  note - not a true guid. I prepend 'g' because 
	  the ID of an element cannot start with a numeral
	*/
	
	function generateGuid() {
	  var S4 = function S4() {
	    return ((1 + Math.random()) * 0x10000 | 0).toString(16).substring(1);
	  };
	  return 'g' + (S4() + S4() + '-' + S4() + '-' + S4() + '-' + S4() + '-' + S4() + S4() + S4());
	}
	

In the @containerUtils section:


	function elementIsChildOfElement(child, potentialParent) {
	  while (child) {
	    if (child === potentialParent) {
	      return true;
	    }
	
	    child = child.parentNode;
	  }
	
	  return false;
	}
	
	function createFieldset(label) {
	  var fieldset = document.createElement('fieldset');
	  var legend = document.createElement('legend');
	  legend.classList.add('legend'); // for easy lookup regardless of mode
	  legend.id = (0, _guidUtils.generateGuid)();
	  legend.innerText = label;
	  fieldset.appendChild(legend);
	  return fieldset;
	}
	
	function createLiveRegion() {
	  var level = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 'polite';
	  var classes = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : [];
	
	  var output = document.createElement('span');
	  classes.forEach(function (c) {
	    return output.classList.add(c);
	  });
	  output.id = (0, _guidUtils.generateGuid)();
	  output.setAttribute('aria-live', level);
	  output.classList.add('deque-visuallyhidden');
	  output.innerText = '';
	  output.notify = function (text) {
	    // TODO: Clean this up...no need to extend the element prototype
	    while (output.firstChild) {
	      output.removeChild(output.firstChild);
	    }
	    var msg = document.createElement('div');
	    msg.innerHTML = text;
	    output.appendChild(msg);
	  };
	
	  return output;
	}
	

Note: No additional JavaScript initialization code is necessary for this pattern. All elements with class="deque-checkbox" will be initialized automatically by the external JavaScript file.

CSS

Required: The complete CSS file (for all patterns in the library): deque-patterns.min.css

Key styles within the CSS file (other styles may also be necessary):


.deque-checkbox-label {
  vertical-align: middle;
}
.deque-checkbox-label:hover {
  cursor: default;
}
.deque-checkbox-aria[role='checkbox'] {
  user-select: none;
}
.deque-checkbox-aria[role='checkbox'].deque-checkbox-focused {
  outline: none;
}
.deque-checkbox-aria[role='checkbox'].deque-checkbox-focused .deque-checkbox-indicator {
  outline: 1px dashed #000000;
}
.deque-checkbox-aria[role='checkbox'] .deque-checkbox-indicator {
  height: 20px;
  left: 0;
  width: 20px;
  line-height: 20px;
  box-shadow: inset 0 0 0 1px #000000, inset 0 0 0 10px transparent;
  top: 0;
  display: inline-block;
  margin-right: 10px;
  position: relative;
  vertical-align: middle;
  border: 1px solid transparent;
}
.deque-checkbox-aria[role='checkbox'] .deque-checkbox-indicator:focus {
  outline: none;
  border: 1px dashed #000000;
}
.deque-checkbox-aria[role='checkbox'][aria-checked='true'] .deque-checkbox-indicator {
  box-shadow: inset 0 0 0 10px #0078d7;
}
.deque-checkbox-aria[role='checkbox'][aria-checked='true'] .deque-checkbox-indicator:after {
  content: '\E8FB';
  font-family: 'mwf-glyphs';
  color: #ffffff;
  font-size: 16px;
  padding-left: 2px;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
}
.deque-checkbox-aria[role='checkbox'][aria-checked='mixed'] .deque-checkbox-indicator {
  box-shadow: inset 0 0 0 10px #0078d7;
}
.deque-checkbox-aria[role='checkbox'][aria-checked='mixed'] .deque-checkbox-indicator:after {
  content: '\E738';
  font-family: 'mwf-glyphs';
  color: #ffffff;
  font-size: 16px;
  padding-left: 2px;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
}
.deque-checkbox-tristate-group {
  margin: 0;
  padding: 10px;
}
.deque-checkbox-tristate[role='checkbox'] {
  cursor: default;
  user-select: none;
}
.deque-checkbox-tristate[role='checkbox'].deque-checkbox-focused {
  outline: none;
}
.deque-checkbox-tristate[role='checkbox'].deque-checkbox-focused .deque-checkbox-indicator {
  outline: 1px dashed #000000;
}
.deque-checkbox-tristate[role='checkbox'] .deque-checkbox-indicator {
  height: 20px;
  left: 0;
  width: 20px;
  line-height: 20px;
  box-shadow: inset 0 0 0 1px #000000, inset 0 0 0 10px transparent;
  top: 0;
  display: inline-block;
  margin-right: 10px;
  position: relative;
  vertical-align: middle;
  border: 1px solid transparent;
}
.deque-checkbox-tristate[role='checkbox'] .deque-checkbox-indicator:focus {
  outline: none;
  border: 1px dashed #000000;
}
.deque-checkbox-tristate[role='checkbox'][aria-checked='true'] .deque-checkbox-indicator {
  box-shadow: inset 0 0 0 10px #0078d7;
}
.deque-checkbox-tristate[role='checkbox'][aria-checked='true'] .deque-checkbox-indicator:after {
  content: '\E8FB';
  font-family: 'mwf-glyphs';
  color: #ffffff;
  font-size: 16px;
  padding-left: 2px;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
}
.deque-checkbox-tristate[role='checkbox'][aria-checked='mixed'] .deque-checkbox-indicator {
  box-shadow: inset 0 0 0 10px #0078d7;
}
.deque-checkbox-tristate[role='checkbox'][aria-checked='mixed'] .deque-checkbox-indicator:after {
  content: '\E738';
  font-family: 'mwf-glyphs';
  color: #ffffff;
  font-size: 16px;
  padding-left: 2px;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
}
.deque-checkbox-tristate-children {
  margin-left: 10px;
}

Fonts

Note: You will need to edit the src for font-family:'mwf-glyphs' in the external CSS file.

Implementation Instructions

Step 1: Add Dependencies

CSS: Add deque-patterns.min.css in the <head> of the document.

<link rel="stylesheet" type="text/css" href="deque-patterns.min.css"></li>

JavaScript: Add a script link to deque-patterns.min.js to the bottom of the page.

<script type="text/javascript" src="deque-patterns.min.js"></script>

Step 2: Add HTML

  • Wrap the code in a <p> container.
    • Create a <div> or <span> container. Add the class="deque-checkbox" for styling purposes and so the javascript can initialize each checkbox automatically. Also add the attribute aria-labeledby attribute that corresponds with the checkbox's label ID. This container creates the box that becomes checked when selected.
    • Add a container with a unique ID. The inner text will be the content of the checkbox.