create butterworth hpf in javascript

index.tsx
// Define the filter parameters
const cutoffFreq = 1000; // Hz
const order = 4;

// Calculate the filter coefficients
const wc = 2 * Math.PI * cutoffFreq;
const T = 1 / sampleRate; // sample rate is assumed to be defined
const alpha = Math.sin(wc * T / (2 * order)) / Math.cos(wc * T / (2 * order));
const a = new Array(order + 1).fill(0);
const b = new Array(order + 1).fill(0);
for (let k = 0; k < order / 2; k++) {
  const theta = Math.PI / 2 + k * Math.PI / order;
  const s = alpha * Math.sin(theta);
  const c = alpha * Math.cos(theta);
  const alpha2 = 2 * Math.sqrt(2) * s * c;
  const beta = Math.pow(s, 2) - Math.pow(c, 2);
  a[k] = alpha2 + beta;
  a[order - k] = alpha2 - beta;
  b[k] = Math.pow(2, order - 1) * (Math.pow(alpha, 2) + Math.pow(s, 2) - Math.pow(c, 2));
  b[order - k] = -b[k];
}
if (order % 2 == 1) {
  const alpha2 = 2 * alpha;
  a[Math.floor(order / 2)] = Math.pow(alpha, 2);
  b[Math.floor(order / 2)] = Math.pow(alpha, order);
}

// Implement the filter function
function butterworthHPF(input) {
  let output = 0;
  for (let k = 0; k <= order; k++) {
    output += b[k] * input[k] - a[k] * output[k];
  }
  return output;
}
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