please help me to resolve my issue. For user experience i must add button in sharepoint display form that will open item for editing. I can add button with this script   but i dont know how add action.
Use below steps:
On display form get Item ID from url using query string parameters.
Add button in on page using CEWP.
On button click write a function and in this function redirect current page to edit form by creating link something like below:
itemId is the ID of item found from step 1.