native audio resampler use OfflineAudioContext

resample_oac.js

function supportedSampleRates() {
    return [4000, 8000, 16000, 32000, 44100, 48000, 96000].filter(supportsSampleRate);
}

function supportsSampleRate(sampleRate) {
  try {
      var l = new OfflineAudioContext(1, sampleRate, sampleRate);
      return true;
  }
  catch(e){
      return false;
  }
  return true;
}

function f2i(floats){
  var ints=[];
  var count = floats.length;
  for (var i = 0; i < count; i++) {
    ints[i] = floats[i] < 0 ? floats[i] * 32768 : floats[i] * 32767;   
  }
  return ints;
}

/**
 * Resample using OfflineAudioContext
 */
function OACX(channels, inBuffer, inNumSamples, inSampleRate, outSampleRate, cb){
  var o = new OfflineAudioContext(channels, inNumSamples, outSampleRate);
  
  // create audio buffer
  var b = o.createBuffer(channels, inNumSamples, inSampleRate);

  // copy data
  for (var channel = 0; channel < channels; channel++) {
      var buf = b.getChannelData(channel);
      for (var i = 0; i < durationInSamples; i++) {
         buf[i] = inBuffer[i];
      }
  }
  //b.getChannelData(0).set(inBuffer);

  /* Play it from the beginning. */
  var source = o.createBufferSource();
  source.buffer = b;
  source.start(0);
  o.oncomplete = function(audiobuffer) {
    /* audiobuffer contains resampled audio, use
     * audiobuffer.getChannelData(x) to get an ArrayBuffer for
     * channel x.
     */
     cb(audiobuffer);
  }

  /* Start rendering as fast as the machine can. */
  o.startRendering();
}

durationInSamples is not defined. I suppose it is same asinNumSamples?

I believe you need to connect source to offline context
source.connect(o.destination);