function i2f(i) {
  var x = new Int32Array(1);
  var y = new Float32Array(x.buffer);
  x[0] = i;
  return y[0];
}

function f2i(f) {
  var x = new Float32Array(1);
  var y = new Int32Array(x.buffer);
  x[0] = f;
  return y[0];
}

console.log(f2i(NaN), f2i(i2f(2143289344)));
console.log(f2i(-NaN), f2i(i2f(-4194304)));