checkNatives

checkNatives.js

function isNativeFunction(fn) {
  return typeof fn === 'function' && fn.toString && !fn.hasOwnProperty('toString') &&
      /\[native code\]/.test(String(fn))
}
function checkNatives(fns) {
  var results = []
  for (var i = 0; i < fns.length; i++) {
    results[i] = {
      fn: fns[i],
      native: isNativeFunction(fns[i])
    }
  }
  return results
}
console.info(checkNatives([setTimeout, XMLHttpRequest]))