metalsmith-start/lib/debounce.js

var now = Date.now || function now () { return new Date().getTime() }

module.exports = debounce

function debounce (func, wait, immediate) {
  var timer, context, timestamp, result
  var args = []
  if (wait == null) wait = 100

  function onTimeout () {
    var elapsed = now() - timestamp

    if (elapsed < wait && elapsed > 0) {
      timer = setTimeout(onTimeout, wait - elapsed)
    } else {
      timer = null
      if (!immediate) {
        result = call()
        if (!timer) reset()
      }
    }
  }

  function call () {
    return func.call(context, args)
  }

  function reset () {
    context = null
    args = []
  }

  return function debounced () {
    context = this
    args.push([].slice.call(arguments))
    timestamp = now()
    var callNow = immediate && !timer
    if (!timer) timer = setTimeout(onTimeout, wait)
    if (callNow) {
      result = call()
      reset()
    }

    return result
  }
}