const recordNode = audioContext.createScriptProcessor(bufferSize, 2, 2);

// an array for each channel
const recording = [[], []];

// note: we are filling recording with `chunks` here, so
// the chunks would need to be reassembled into a single buffer when you're ready to export
recordNode.onaudioprocess = ((e) => {
  recording[0].push(new Float32Array(e.inputBuffer.getChannelData(0)));
  recording[1].push(new Float32Array(e.inputBuffer.getChannelData(1)));
});