koTristateCheckboxes

Tristate Boolean extension for knockout.js

<input type="checkbox" data-bind="tristate: someTristate" />

It's so easy to create a tristate Checkbox with knockout.js and this plugin...

Sample Markup

<html>
	<head>
		<script type="text/javascript" language="javascript" src="knockout-2.3.0.js"></script>
		<script type="text/javascript" language="javascript" src="tristateInputField.js"></script>
		<link type="text/css" rel="stylesheet" href="tristateInputField.css">
	</head>
	<body>
		<div id="__test">
			<input type="checkbox" data-bind="tristate: someTristate" />
		</div>
		<script>
			(function(){
				var __test = {someTristate : ko.tristateBoolean(undefined, true)};
				ko.applyBindings(__test, document.getElementById('__test'));
			})();
		</script>
	</body>
</html>

Known Limitations

requires at least a browser that supports transform css-property.
You can't use the css-Selector :checked on the tristate checkbox. It returns a false value (since it can only be true or false)
Use [checked="checked"] for true-ish values
and [tristate="tristate"] for undefined values.

Usage:

data-bind="tristate: someTristate"

the "tristate" binding accepts a "ko.tristateBoolean" or a "ko.observable"-wrapped "ko.tristateBoolean"

data-bind="tristate: someTristate, tristateFontSize: anyValidFontSizeValue"

You can also specify a default fontSize, which is used if the fontSize is not set or below "8px"
(otherwise its forced to be at least 8px or set to 16px if font size is not set)
Example values for anyValidFontSizeValue:

12px
1em
1ex
1in
3cm
40mm
12pc
12pt
xx-small
x-small
small
medium
large
x-large
xx-large
smaller
larger

ko.tristateBoolean

var tribool = ko.tristateBoolean(initialValue, defaultValue);

Creates a tristateBoolean.

The initial value is set as the value of the tristateBoolean.

allowed values are:

true
false
undefined or null

The default value is returned when converting the tristateBoolean back to a boolean and
the tristateBoolean has no value.

allowed values are:

true
false

tribool.defaultValue(/*bool?*/ defaultValue);

Get or set the default value.

tribool.hasValue();

Check if tribool has a value (true or false, but not undefined).

tribool.getWithDefaultifNull(/*bool?*/ defaultValue);

Get value as boolean.

Returns the tribool's default value (or if provided the defaultValue argument) if tribool has no value.

tribool.and(/*tribool?*/ defaultValue);

And (&&) two tristateBooleans.

tribool.or(/*tribool?*/ defaultValue);

Or (||) two tristateBooleans.

tribool.not();

Returns not (!) the value of this tristateBoolean.

helper functions

ko.isTristateBoolean(value);

Checks if value is a tristateBoolean.

ko.utils.unwrapTristateBoolean(value);

Unwraps an tristateBoolean or returns value.

ko.utils.getValidTristateBooleanValue(value);

Returns value if valid value (true/false/undefined) or the bool representation of value.

Credits

get computed css Properties in JS
(http://stackoverflow.com/a/1955160)
Super amazing, cross browser property function
(http://johndyer.name/native-browser-get-set-properties-in-javascript/)
Cross-browser CSS3 Image-Free Custom Checkbox
(http://kubyshkin.ru/web/cross-browser-css3-image-free-custom-checkbox/)

License

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

sebikeller / koTristateCheckboxes