How to Make date Picker field non-editable using java script. currently we are u

What you are saying is combination of two sets of information. If I understood you correctly, you are displaying mixed content in a grid where some can and some cannot be modified. If that's the case, there are the two OOTB options you can do.
Display the content in a paging grid so users selects the row they want to modify and make the changes in a following form. This will give you the option to control the field based on the status of the row selected.
Option 2: Allow all the date field to be editable but put an instruction on top of the grid indicating changing date for records that cannot be modified (for e.g. completed) will throw a validation error. Then validate the change when user submits the form and if the user had made an error by editing one such row, bring the user back to the same form highlighting the error.

What you are saying is combination of two sets of information. If I understood you correctly, you are displaying mixed content in a grid where some can and some cannot be modified. If that's the case, there are the two OOTB options you can do.
Display the content in a paging grid so users selects the row they want to modify and make the changes in a following form. This will give you the option to control the field based on the status of the row selected.
Option 2: Allow all the date field to be editable but put an instruction on top of the grid indicating changing date for records that cannot be modified (for e.g. completed) will throw a validation error. Then validate the change when user submits the form and if the user had made an error by editing one such row, bring the user back to the same form highlighting the error.