// 減緩呼叫function的時間

function debounce(func, wait = 20, immediate = true) {

  console.log('debounce~~~~in');

  var timeout;

  return function() {

    console.log('function~~~~in');

    var context = this, args = arguments;

    var later = function() {

      timeout = null;

      if (!immediate) func.apply(context, args);

    };

    var callNow = immediate && !timeout;

    clearTimeout(timeout);

    timeout = setTimeout(later, wait);

    if (callNow) func.apply(context, args);

  };

}

​

​

function handleShowImage(e){

//   console.log('handleShowImage');

//   console.timeEnd();

//   console.time();

}

​

​

​

// window.addEventListener('scroll', handleShowImage);

​

window.addEventListener('scroll', debounce(handleShowImage,0,true));