peaknormalize.js

function peakNormalize(arr) {
  let peakHigh = 0,
    peakLow = 0;
  for (let i = 0; i < arr.length; i++) {
    peakHigh = Math.max(peakHigh, arr[i]);
    peakLow = Math.min(peakLow, arr[i]);
  }
  if (peakHigh > 0.7 || peakLow < -0.7) {
    let ratio = Math.max(peakHigh, -peakLow) / 0.7;
    for (let i = 0; i < arr.length; i++) {
      arr[i] /= ratio;
    }
  }
}