if a jQuery function throws "is not a function" error it's because that function is not available when you call it. Available means browser hasn't loaded it, so either you don't have script files in correct order or a path to file problem

jQueryUI site explains the order, path easy to check in browser.

Priya wrote:

hi i am getting this error when i was trying to use the jquery
datepicker widget.Can you please help me to solve this issue?