I have this function:
function doStuff(range, file) {
var fr = new FileReader();
var hash = '';
fr.onload = function (e) {
var out = "stuff happens here";
hash = asmCrypto.SHA256.hex(out);
return hash;
};
fr.readAsArrayBuffer(file);
return hash;
}
Right now, the function completes before the onload event is finished, so doStuff always returns "". I think a callback is what I need, but I'm new to javascript, and I can't wrap my mind around how to implement it in this case.