How to pass pure base64?

Question

JavaScript

when loading a JSON file in the input type file in event.target.result - a string like data:application/json;base64,ew0KICAiaGVhZGVyIjogew0KICAgICJsYXVuY2hwYWQiOiAiTGF1bmNocGFkIiwNCiAgICAicHJpc20iOiAiUHJpc20iLA0KICAgI is passed

how to remove this prefix data:application/json;???? to leave base64,ew0KICAiaGVhZGVyIjogew0KICAgICJsYXVuY2hwYWQiOiAiTGF1bmNocGFkIiwNCiAgICAicHJpc20iOiAiUHJpc20iLA0KICAgI

Answer 1

test.replace(/^data:\w+\/\w+;/, '')
where test is your string

Answer 2

If you want to insert this base64 file into the input field, then you asked the wrong question, because removing the prefix will not help you here, and inserting is done in a completely different way.