I am using select2 (http://ivaynberg.github.io/select2/) for my tagging input. from the example in using select2 tagging the code is look like this.
$(\"#e1
You can initialize the Select2 control by providing a value for the hidden input:
And you can set the value of the Select2 control by passing an array to the 'val' method:
$('#tagSelect').select2('val', ['brown','red','green']);
jsfiddle demo