var $field = $(this); if ($field.is('input')) { alert(1); if ($field.attr('type') == 'checkbox') { alert(2); if ($field.attr('value') == "true") return $field.attr('checked'); } return $field.val(); } I want to check if value of checkbox is true i add attribute checked = checked for checkbox. but my code is wrong. please help me.thanks
You can use the :checked selector to greatly help with this.
var $field = $(this); return $field.is(':checked'); This will return a proper bool. If you return the attr('checked') or the val(), you'll end up with a string, which is probably not what you want.
Change the condition to
$("input:checkbox").val() == "true" and for checking the checkbox you can use
$("input:checkbox").attr ( "checked" , true ); You can select a checkbox using
$("input:checkbox") and value using
$("input:checkbox").val() If you want to check all the checkboxes with attribute value true then you can use
$(document).ready ( function () { var checkBoxes = $("input:checkbox"); checkBoxes.each ( function () { if ( $(this).val() == "true" ) { $(this).attr ( "checked" , true ); } }); }); 
.attr('checked') will return true for checked and undefined for unchecked
CORRECTION:
.attr("checked") will return "checked" if checked (not true), "undefined" if not checked.
If you want a true/false then you have to do something like this:
$("#checker").attr("checked")=="checked" 