fft

#!/usr/bin/env node

const dsp = require('../lib/dsp.js');

// Edit the following parameters as required
const SAMPLING_RATE = 44100;
const NUMBER_OF_SAMPLES = 32768;

// Adapt this function to generate sample values
function generateSample(element, index) {
  return Math.cos(440 * index * 2 * Math.PI / SAMPLING_RATE); // 440Hz (A4)
}

// The samples will be generated using the above function
const samples = Array(NUMBER_OF_SAMPLES).fill().map(generateSample);

// Start timing the operation
let startTime = Date.now();

// Perform a FFT on the samples
let fft = dsp.fft(samples, SAMPLING_RATE);

// Display the operation duration
console.log('Completed in', Date.now() - startTime, 'ms');

// Prepare variables to highlight the peak
let peakFrequency, peakMagnitude = 0;

// Iterate through all frequency bins to find the peak magnitude
for(let bin = 0; bin < fft.numberOfBins; bin++) {
  if(fft.magnitudes[bin] > peakMagnitude) {
    peakFrequency = fft.frequencies[bin];
    peakMagnitude = fft.magnitudes[bin];
  }
}

// Print the peak frequency/magnitude
console.log('Peak magnitude of ' + peakMagnitude.toPrecision(4) + ' at ' +
            peakFrequency.toPrecision(4) + 'Hz');