Jquery tagit not working for dynamic content.

Jquery tagit not working for dynamic content.

Hi all,
I am using tagit of jqueryui.
Its working if I am using like this.
var desigvalues =["Actor","Anchor","Dancer","Singer"];
jQuery(' #singleFieldTags ').tagit({
availableTags: desigvalues,
singleField: true,
singleFieldNode: jQuery(' #mySingleField '),
allowSpaces: true,
placeholderText: "Type your designation!",
autocomplete: {delay: 0, minLength:1}

});

Same if I am making this dynamic its not working

var desigvalues;
jQuery.ajax({
type: 'POST',
url: "/user/edit/getdesignationlist",
data: "{}",
dataType: "json",
async : false,
success: function(data) {
desigvalues='['+data+']';
}
});
jQuery(' #singleFieldTags ').tagit({
availableTags: desigvalues,
// This will make Tag-it submit a single form value, as a comma-delimited field.
singleField: true,
singleFieldNode: jQuery(' #mySingleField '),
allowSpaces: true,
placeholderText: "Type your designation!",
autocomplete: {delay: 0, minLength:1}

});
the autocomplete list coming wrongly.
Any suggestion why this is happening.
thanks