Posting binary WAV file from javascript to R shiny server.

script.js

// See also http://stackoverflow.com/a/27228544/2596404

// Blob is your binary data.
// blob = ...;

// Encode the data and post to server.
var reader = new FileReader();
reader.readAsDataURL(blob);
reader.onloadend = function() {
    base64data = reader.result;

    // Trigger the change event on the form field to activate the reactive field on the server.
    $('#audio').val(base64data).change();
    // Submit the form by triggering the click event on the button.
    $('#btnUpload').click();
}

server.R

shinyServer(function(input, output, session) {
  observeEvent(input$btnUpload, {
    # Decode wav file.
    audio <- input$audio
    audio <- gsub('data:audio/wav;base64,', '', audio)
    audio <- gsub(' ', '+', audio)
    audio <- base64Decode(audio, mode = 'raw')
    
    # Save to file on server.
    inFile <- list()
    inFile$datapath <- paste0('temp', sample(1:100000, 1), '.wav')
    inFile$file <- file(inFile$datapath, 'wb')
    writeBin(audio, inFile$file)
    close(inFile$file)

    # ...
  }
}

ui.html

<input id='audio' type='text' style='display: none;' />
<input id='btnUpload' type='button' style='display: none;' />

Thank you very much.