Convert to base64 and send to server?

Question

React Native

Good day. We get a photo -> convert it to base64 -> send it to the server. Please help me implement this functionality. I work through react native expo. I know that expo imagepicker has a built-in method that converts to base64, I use it. But I'm not sure that it works correctly (can you advise an alternative. Below is the code for converting the image and sending it to the server (this code does not work) help me figure out what the problem is?