debounce.js

// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds. If `execAsap` is passed, trigger the function on the
// leading edge, instead of the trailing.
export function debounce (func, threshold, execAsap) {
  var timeout

  return function debounced () {
    var obj = this
    var args = arguments

    function delayed () {
      if (!execAsap) func.apply(obj, args)
      timeout = null
    }

    if (timeout) clearTimeout(timeout)
    else if (execAsap) func.apply(obj, args)

    timeout = setTimeout(delayed, threshold || 100)
  }
}