jQuery 1.6+

Use the new .prop() method:

[code]$(‘.myCheckbox’).prop(‘checked’, true);
$(‘.myCheckbox’).prop(‘checked’, false);[/code]

jQuery 1.5.x and below

The .prop() method is not available, so you need to use .attr().

[code]$(‘.myCheckbox’).attr(‘checked’, true);
$(‘.myCheckbox’).attr(‘checked’, false);[/code]

Note that this is the approach used by jQuery’s unit tests prior to version 1.6 and is preferable to using

[code]$(‘.myCheckbox’).removeAttr(‘checked’);[/code]

since the latter will, if the box was initially checked, change the behaviour of a call to .reset() on any form that contains it – a subtle but probably unwelcome behaviour change.

For more context, some incomplete discussion of the changes to the handling of the checked attribute/property in the transition from 1.5.x to 1.6 can be found in the version 1.6 release notes and the Attributes vs. Properties section of the .prop() documentation.