How to strip type from Javascript FileReader base64 string?

let reader: FileReader = new FileReader();
 
 reader.onloaded = (e) => {
    let base64String = reader.result.split(',').pop();
 };

or

let base64String = /,(.+)/.exec(reader.result)[1];

The following functions will achieve your desired result:

var base64result = reader.result.split(',')[1];

This splits the string into an array of strings with the first item (index 0) containing data:image/png;base64 and the second item (index 1) containing the base64 encoded data.

Another solution is to find the index of the comma and then simply cut off everything before and including the comma:

var base64result = reader.result.substr(reader.result.indexOf(',') + 1);

See JSFiddle.

You can try splitting your data using ;base64,.

// In here you are getting the data type. Ex - png, jpg, jpeg, etc. You can use this for any further purposes.
var dataType = reader.result.split(';base64,')[0];

// In here you are getting the base64 string and you can use this for your purpose.
var base64result = reader.result.split(';base64,')[1];