图片懒加载imgLazyLoading.js使用详解

//懒加载对象目标代码
<img originalSrc="__PUBLIC__/images/home/icon_pingtuan.png">
//引用本地js
<script src="/UploadFiles/2021-04-02/imgLazyLoading.min.js">

2、js代码
imgLazyLoading.min.js


jQuery.fn.extend({
 delayLoading: function (a) {
  function g(d) {
   var b, c;
   if (a.container === undefined || a.container === window) {
    b = $(window).scrollTop();
    c = $(window).height() + $(window).scrollTop()
   } else {
    b = $(a.container).offset().top;
    c = $(a.container).offset().top + $(a.container).height()
   }
   return d.offset().top + d.height() + a.beforehand >= b && c >= d.offset().top - a.beforehand
  }

  function h(d) {
   var b, c;
   if (a.container === undefined || a.container === window) {
    b = $(window).scrollLeft();
    c = $(window).width() + $(window).scrollLeft()
   } else {
    b = $(a.container).offset().left;
    c = $(a.container).offset().left + $(a.container).width()
   }
   return d.offset().left + d.width() + a.beforehand >= b && c >= d.offset().left - a.beforehand
  }

  function f() {
   e.filter("img[" + a.imgSrcAttr + "]").each(function (d, b) {
    if ($(b).attr(a.imgSrcAttr) !== undefined && $(b).attr(a.imgSrcAttr) !== null && $(b).attr(a.imgSrcAttr) !== "" && g($(b)) && h($(b))) {
     var c = new Image;
     c.onload = function () {
      $(b).attr("src", c.src);
      a.duration !== 0 && $(b).hide().fadeIn(a.duration);
      $(b).removeAttr(a.imgSrcAttr);
      a.success($(b))
     };
     c.onerror = function () {
      $(b).attr("src",
       a.errorImg);
      $(b).removeAttr(a.imgSrcAttr);
      a.error($(b))
     };
     c.src = $(b).attr(a.imgSrcAttr)
    }
   })
  }

  a = jQuery.extend({
   defaultImg: "",
   errorImg: "",
   imgSrcAttr: "originalSrc",
   beforehand: 0,
   event: "scroll",
   duration: "normal",
   container: window,
   success: function () {
   },
   error: function () {
   }
  }, a || {});
  if (a.errorImg === undefined || a.errorImg === null || a.errorImg === "")a.errorImg = a.defaultImg;
  var e = $(this);
  if (e.attr("src") === undefined || e.attr("src") === null || e.attr("src") === "")e.attr("src", a.defaultImg);
  f();
  $(a.container).bind(a.event, function () {
   f()
  })
 }
});



imgLazyLoading.js


$(function () {
 $("img").delayLoading({
  //defaultImg: "__PUBLIC__/images/img/loading.gif",   // 预加载前显示的图片
  errorImg: "",      // 读取图片错误时替换图片(默认：与defaultImg一样)
  imgSrcAttr: "originalSrc",   // 记录图片路径的属性(默认：originalSrc，页面img的src属性也要替换为originalSrc)
  beforehand: 0,      // 预先提前多少像素加载图片(默认：0)
  event: "scroll",      // 触发加载图片事件(默认：scroll)
  duration: "normal",     // 三种预定淡出(入)速度之一的字符串("slow", "normal", or "fast")或表示动画时长的毫秒数值(如：1000),默认:"normal"
  container: window,     // 对象加载的位置容器(默认：window)
  success: function (imgObj) { },  // 加载图片成功后的回调函数(默认：不执行任何操作)
  error: function (imgObj) { }   // 加载图片失败后的回调函数(默认：不执行任何操作)
 });
});



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