Mobile page turning plug in dropload. js (supports Zepto and jQuery)

dropload. js provides the most basic pull-up page turning and pull-down refresh functions. It is basically common to return all data once by the server.
However, the requirement is not that the server returns all the data once, but also supports the functions of paging, searching, sorting, multi-condition filtering and so on. (It is more similar to the interface of Meituan cuisine)

1. Solutions

Improvement 1: Because there are paging, search, sorting, multi-condition filtering functions, may not need to pull up, and there is no data on the page.
For example, search for a name that does not exist on the server.
So, add the interface setting setHasData.

MyDropLoad.prototype.setHasData = function(ishasData) {
  var me = this;
  if (ishasData) {
   me.isData = true;
   me.$domDown.html(me.opts.domDown.domRefresh);
   fnRecoverContentHeight(me);
  } else {
   me.isData = false;
   me.$domDown.html(me.opts.domDown.domNoData);
   fnRecoverContentHeight(me);
  }
 }; 

Improvement 2: 1 bug is also raised by the above problem. Select different filter conditions, then pull up and load more, and there is no response at this time.
The reason is more complex, for example: Choose different screening conditions, the amount of data is not 1, if resetload is not implemented, then the page of the pull-up calculation distance there is a problem.
1. As long as API is sent to the server, resetload must be executed regardless of success or failure. If it is successful, resetload needs to be loaded after all the newly added data.
2. Change resetload as follows, adding the method that calls to calculate the screen size.

MyDropLoad.prototype.resetload = function() {
  var me = this;
  if (me.direction == 'down' && me.upInsertDOM) {
   me.$domUp.css({ 'height': '0' }).on('webkitTransitionEnd mozTransitionEnd transitionend', function() {
    me.loading = false;
    me.upInsertDOM = false;
    $(this).remove();
    fnRecoverContentHeight(me);
   });
  } else if (me.direction == 'up') {
   me.loading = false;
   if (me.isData) {
    me.$domDown.html(me.opts.domDown.domRefresh);
    fnRecoverContentHeight(me);
   } else {
    me.$domDown.html(me.opts.domDown.domNoData);
   }
  }
 } 

3. To solve the above two problems, 90% of the problems are basically solved, and the other one is the treatment after setHasData (false). (Assuming 20 count per page)
bug: Set setHasData (false) when screening condition 1: 20 pieces of data are returned and pull-up load returns more than 10 pieces of data. Select Filter 2, return 20 pieces of data, pull up and load, and you will be surprised to find that it can't be pulled.
After why: setHasData (false), the state stays in a state with no more data. At this time, the pull-up load should be locked. After changing the filter criteria, the lock is not unlocked, so the pull-up load cannot be lifted.
Solution: setHasData (true) needs to be set every time you change search criteria, filter criteria, sort, and so on.

2. Call the method
The overall page logic is complicated. Here, explain it once as a whole.
1. Select the DIV to pull up and load, and add the calling method.
Precautions:
(1) Remember to save the returned object.
(2) LoadDownFn pull-up after the callback, here their own logic to deal with. When I turn pages here, I send API, add 20 to offset in API parameter, and then send API.
(3) resetload is required regardless of whether API returns a failed success.
It is emphasized here:
The fetchData function call sends API. self. moreFund. resetload () is required for failure or success.
And if it fails, call self. moreFund. resetload () directly. When the new data is returned, HTML should be dynamically loaded with JS, and self. moreFund. resetload () should be executed after loading.

self.moreFund = $('#table-fundlist').dropload({
 scrollArea: window,
 domDown: {
  domClass: 'dropload-down',
  domRefresh: '<div class="dropload-refresh"><img class="drop-up-icon" src="images/dropload_up.png"><span> Pull up and load more </span></div>',
  domLoad: '<div class="dropload-load"><img class="loading-icon" src="images/droploading.gif"></div>',
  domNoData: ''
 },
 loadDownFn: function() {
  self.apiParams.offset += 20;
  self.fetchData(true);
 }
}); 

2. Detailed explanation of setHasData
(1) When true needs to be set.
Before the non-page turning API triggers. That is, select a new filter, select a new search field, and select a new sort field. setHasData (true) is required at this time.
this.moreFund.setHasData(true);
(2) When to set false.
After the server returns the data, compare the number of items returned by the server with whether the number of items sent by API is 1 or not, and set setHasData (false) if it is not 1.

 if (data.length < this.apiParams.count){      
 this.moreFund.setHasData(false);
 this.moreFund.lock();
} 

3. Detailed explanation of lock and unlock
(1) When to set lock.
After the server returns the data, compare the number of entries returned by the server with whether the number of entries sent by API is 1 or not, and set lock () if it is not 1.
lock () needs to be set when the current page state does not need to pull up and load. For example, enter the status in the search box.
(2) When to set unlock.
There is only one place to call. Set unlock before sending API.

if (self.moreFund) {
 self.moreFund.unlock();
} 

3. JS and CSS source code

js:

(function($) {
 'use strict';
 var win = window;
 var doc = document;
 var $win = $(win);
 var $doc = $(doc);
 $.fn.dropload = function(options) {
  return new MyDropLoad(this, options);
 };
 var MyDropLoad = function(element, options) {
  var me = this;
  me.$element = $(element);
  me.upInsertDOM = false;
  me.loading = false;
  me.isLockUp = false;
  me.isLockDown = false;
  me.isData = true;
  me._scrollTop = 0;
  me.init(options);
 };
 MyDropLoad.prototype.init = function(options) {
  var me = this;
  me.opts = $.extend({}, {
   scrollArea: me.$element,
   domUp: {
    domClass: 'dropload-up',
    domRefresh: '<div class="dropload-refresh"><img class="drop-down-icon" src="../images/dropload_down.png"><span> Drop-down refresh </span></div>',
    domUpdate: '<div class="dropload-update"><img class="drop-up-icon" src="../images/dropload_up.png"><span> Release updates </span></div>',
    domLoad: '<div class="dropload-load"><img class="loading-icon" src="../images/droploading.gif"></div>'
   },
   domDown: {
    domClass: 'dropload-down',
    domRefresh: '<div class="dropload-refresh"><img class="drop-up-icon" src="../images/dropload_up.png"><span> Pull up and load more </span></div>',
    domLoad: '<div class="dropload-load"><img class="loading-icon" src="../images/droploading.gif"></div>',
    domNoData: ''
     //domNoData : '<div class="dropload-noData"><span> Data is not available at present </span></div>'
   },
   distance: 50, //  Pulling distance 
   threshold: '', //  Advance loading distance 
   loadUpFn: '', //  Above function
   loadDownFn: '' //  Below function
  }, options);

  if (me.opts.loadDownFn != '') {
   me.$element.append('<div class="' + me.opts.domDown.domClass + '">' + me.opts.domDown.domRefresh + '</div>');
   me.$domDown = $('.' + me.opts.domDown.domClass);
  }

  if (me.opts.scrollArea == win) {
   me.$scrollArea = $win;
   me._scrollContentHeight = $doc.height();
   me._scrollWindowHeight = doc.documentElement.clientHeight;
  } else {
   me.$scrollArea = me.opts.scrollArea;
   me._scrollContentHeight = me.$element[0].scrollHeight;
   me._scrollWindowHeight = me.$element.height();
  }

  $win.on('resize', function() {
   if (me.opts.scrollArea == win) {
    me._scrollWindowHeight = win.innerHeight;
   } else {
    me._scrollWindowHeight = me.$element.height();
   }
  });

  me.$element.on('touchstart', function(e) {
   if (!me.loading) {
    fnTouches(e);
    fnTouchstart(e, me);
   }
  });
  me.$element.on('touchmove', function(e) {
   if (!me.loading) {
    fnTouches(e, me);
    fnTouchmove(e, me);
   }
  });
  me.$element.on('touchend', function() {
   if (!me.loading) {
    fnTouchend(me);
   }
  });

  me.$scrollArea.on('scroll', function() {
   me._scrollTop = me.$scrollArea.scrollTop();
   fnRecoverContentHeight(me)
   if (me.opts.threshold === '') {
    me._threshold = Math.floor(me.$domDown.height() * 1 / 3);
   } else {
    me._threshold = me.opts.threshold;
   }
   if (me.opts.loadDownFn != '' && !me.loading && !me.isLockDown && me._threshold != 0 && (me._scrollContentHeight - me._threshold) <= (me._scrollWindowHeight + me._scrollTop)) {
    fnLoadDown();
   }
  });

  function fnLoadDown() {
   me.direction = 'up';
   me.$domDown.html(me.opts.domDown.domLoad);
   me.loading = true;
   me.opts.loadDownFn(me);
  }
 };

 function fnTouches(e) {
  if (!e.touches) {
   e.touches = e.originalEvent.touches;
  }
 }

 function fnTouchstart(e, me) {
  me._startY = e.touches[0].pageY;
  me.touchScrollTop = me.$scrollArea.scrollTop();
 }

 function fnTouchmove(e, me) {
  me._curY = e.touches[0].pageY;
  me._moveY = me._curY - me._startY;

  if (me._moveY > 0) {
   me.direction = 'down';
  } else if (me._moveY < 0) {
   me.direction = 'up';
  }

  var _absMoveY = Math.abs(me._moveY);

  if (me.opts.loadUpFn != '' && me.touchScrollTop <= 0 && me.direction == 'down' && !me.isLockUp) {
   e.preventDefault();

   me.$domUp = $('.' + me.opts.domUp.domClass);
   if (!me.upInsertDOM) {
    me.$element.prepend('<div class="' + me.opts.domUp.domClass + '"></div>');
    me.upInsertDOM = true;
   }
   fnTransition(me.$domUp, 0);
   if (_absMoveY <= me.opts.distance) {
    me._offsetY = _absMoveY;
    me.$domUp.html(me.opts.domUp.domRefresh);
   } else if (_absMoveY > me.opts.distance && _absMoveY <= me.opts.distance * 2) {
    me._offsetY = me.opts.distance + (_absMoveY - me.opts.distance) * 0.5;
    me.$domUp.html(me.opts.domUp.domUpdate);
   } else {
    me._offsetY = me.opts.distance + me.opts.distance * 0.5 + (_absMoveY - me.opts.distance * 2) * 0.2;
   }
   me.$domUp.css({ 'height': me._offsetY });
  }
 }

 // touchend
 function fnTouchend(me) {
  var _absMoveY = Math.abs(me._moveY);
  if (me.opts.loadUpFn != '' && me.touchScrollTop <= 0 && me.direction == 'down' && !me.isLockUp) {
   fnTransition(me.$domUp, 300);

   if (_absMoveY > me.opts.distance) {
    me.$domUp.css({ 'height': me.$domUp.children().height() });
    me.$domUp.html(me.opts.domUp.domLoad);
    me.loading = true;
    me.opts.loadUpFn(me);
   } else {
    me.$domUp.css({ 'height': '0' }).on('webkitTransitionEnd transitionend', function() {
     me.upInsertDOM = false;
     $(this).remove();
    });
   }
   me._moveY = 0;
  }
 }

 //  Retrieve document height 
 function fnRecoverContentHeight(me) {
  if (me.opts.scrollArea == win) {
   me._scrollContentHeight = $doc.height();
  } else {
   me._scrollContentHeight = me.$element[0].scrollHeight;
  }
 }

 MyDropLoad.prototype.lock = function(direction) {
  var me = this;
  if (direction === undefined) {
   if (me.direction == 'up') {
    me.isLockDown = true;
   } else if (me.direction == 'down') {
    me.isLockUp = true;
   } else {
    me.isLockUp = true;
    me.isLockDown = true;
   }
  } else if (direction == 'up') {
   me.isLockUp = true;
  } else if (direction == 'down') {
   me.isLockDown = true;
  }
 };

 MyDropLoad.prototype.unlock = function() {
  var me = this;
  me.isLockUp = false;
  me.isLockDown = false;
 };

 MyDropLoad.prototype.setHasData = function(ishasData) {
  var me = this;
  if (ishasData) {
   me.isData = true;
   me.$domDown.html(me.opts.domDown.domRefresh);
   fnRecoverContentHeight(me);
  } else {
   me.isData = false;
   me.$domDown.html(me.opts.domDown.domNoData);
   fnRecoverContentHeight(me);
  }
 };

 MyDropLoad.prototype.resetload = function() {
  var me = this;
  if (me.direction == 'down' && me.upInsertDOM) {
   me.$domUp.css({ 'height': '0' }).on('webkitTransitionEnd mozTransitionEnd transitionend', function() {
    me.loading = false;
    me.upInsertDOM = false;
    $(this).remove();
    fnRecoverContentHeight(me);
   });
  } else if (me.direction == 'up') {
   me.loading = false;
   if (me.isData) {
    me.$domDown.html(me.opts.domDown.domRefresh);
    fnRecoverContentHeight(me);
   } else {
    me.$domDown.html(me.opts.domDown.domNoData);
   }
  }
 };

 function fnTransition(dom, num) {
  dom.css({
   '-webkit-transition': 'all ' + num + 'ms',
   'transition': 'all ' + num + 'ms'
  });
 }
})(window.Zepto || window.jQuery); 

CSS:

.dropload-up,
.dropload-down {
 background-color: #F0EFF5;
 position: relative;
 height: 0;
 overflow: hidden;
}

.dropload-down {
 height: 50px;
 border-top: 1px solid #e5e5e5;
}

.dropload-refresh .drop-up-icon,
.dropload-refresh .drop-down-icon,
.dropload-update .drop-up-icon,
.dropload-update .drop-down-icon {
 vertical-align: text-bottom;
 margin-right: 3px;
 height: 16px;
 width: 12px;
}

.dropload-load .loading-icon {
 vertical-align: middle;
 height: 20px;
 width: 20px;
}

.dropload-refresh span,
.dropload-update span {
 vertical-align: middle;
 line-height: 18px;
 font-size: 16px;
 color: #585858;
}

.dropload-noData {
 border-bottom: 1px solid #e5e5e5;
 background-color: #FFFFFF;
}

.dropload-noData span {
 line-height: 18px;
 font-size: 14px;
 color: #999999;
}

.dropload-refresh,
.dropload-update,
.dropload-load,
.dropload-noData {
 position: absolute;
 width: 100%;
 height: 50px;
 bottom: 0;
 line-height: 50px;
 text-align: center;
}

.dropload-down .dropload-refresh,
.dropload-down .dropload-update,
.dropload-down .dropload-load {
 top: 0;
 bottom: auto;
}