var fft = require('kissfft').fft;

// Input is 1+0i 2+0i 3+0i 4+0i
var input = Float32Array([1, 0, 2, 0, 3, 0, 4, 0]);
var output = Float32Array(input.length);

// input and output must be exactly the same length, must both have an even
// number of elements, and must both be Float32Arrays.
fft(input, output, callback (err, result) {
  // result === output
});

var fft = require('kissfft').fft;

var input = Float32Array([1, 2, 3, 4]);
var output = Float32Array(input.length + 2);

// output must have exactly two elements more than input and input must
// have an even number of elements.
fft(input, output, callback (err, result) {
  // result === output
});