Using jQuery prop() method you can enable or disable a form element. From jQuery 1.6+ you can use jQuery prop() method.
You can enable or disable an elements on a page dynamically with jQuery by setting their attributes accordingly.
For jQuery 1.5 and below the .prop() function doesn’t exist, but .attr() method does similar thing.
Disable a Control:
$( "#elementID" ).prop( "disabled", true );
Enable a Control:
$( "#elementID" ).prop( "disabled", false );
Also Read:
Using .attr():
Set the disabled attribute:
$("input").attr('disabled','disabled');
To enable again you can use .removeAttr():
$("input").removeAttr('disabled');
This will totally remove the disabled attribute from the element instead of blanking it out.
Read jQuery reference for more details.