实现目标:实现瀑布流布局、当滚动条滚动到一定距离时加载图片
瀑布流布局:结合窗口改变 定位第一行的盒子 第二行第一个盒子接到第一行最矮的盒子下面 当接完后更新最矮盒子 以此类推
滚动加载图片:案例是用数组对象实现图片加载 条件是当加载到最后一张图片一半+最后盒子的offsetTop小于等于屏幕的高度+滚动的距离时 加载图片
当窗口更新时:运用onresize事件重置 运用节流使得加载性能提高
html+css
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>瀑布流</title>
<style>
body, h1, h2, h3, h4, h5, h6, hr, p, blockquote, dl, dt, dd, ul, ol, li, pre, form, fieldset, legend,
button, input, textarea, th, td { margin:0; padding:0;border:none;list-style:none; }
body,html{
width: 100%;
height: 100%;
}
#main{
position: relative;
}
.box{
float: left;
padding: 15px 0 0 15px;
}
.pic{
border:1px solid #ccc;
border-radius: 5px;
padding: 10px;
}
.pic img{
width: 150px;
}
</style>
</head>
<body>
<div id="main">
<div class="box">
<div class="pic"><img src="imgs/img01.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img02.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img03.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img04.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img05.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img06.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img07.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img08.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img09.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img10.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img11.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img12.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img13.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img14.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img15.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img16.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img17.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img18.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img19.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img20.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img21.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img22.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img23.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img24.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img25.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img26.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img27.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img28.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img29.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img30.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img31.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img32.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img33.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img34.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img35.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img36.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img37.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img38.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img39.jpg" alt=""></div>
</div>
<div class="box">
<div class="pic"><img src="imgs/img40.jpg" alt=""></div>
</div>
</div>
<script src="js/index.js"></script>
<script src="js/scroll.js"></script>
</body>
</html>
注意:index.js为主要js代码 scroll.js为封装scroll的代码 链接:https://www.jianshu.com/p/6427731bb125
css方面:添加定位
window.onload = function () {
// 1. 实现瀑布流布局
waterFull("main", "box");
// 2. 动态加载图片
var timer1 = null;
window.onscroll = function () {
clearTimeout(timer1);
timer1 = setTimeout(function () {
if(checkWillLoadImage()){
// 2.1 造数据
var dataArr = [
{"src": "img04.jpg"},
{"src": "img06.jpg"},
{"src": "img08.jpg"},
{"src": "img09.jpg"},
{"src": "img10.jpg"},
{"src": "img12.jpg"},
{"src": "img14.jpg"},
{"src": "img16.jpg"},
{"src": "img18.jpg"}
];
// 2.2 创建元素
for(var i=0; i<dataArr.length; i++){
var newBox = document.createElement("div");
newBox.className = "box";
$("main").appendChild(newBox);
var newPic = document.createElement("div");
newPic.className = "pic";
newBox.appendChild(newPic);
var newImg = document.createElement("img");
newImg.src = "images/" + dataArr[i].src;
newPic.appendChild(newImg);
}
// 2.3 重新布局
waterFull("main", "box");
}
}, 200);
};
// 3. 窗口的大小发生改变
var timer = null;
window.onresize = function () {
clearTimeout(timer);
// 节流
timer = setTimeout(function () {
waterFull('main', 'box');
}, 200);
}
};
/**
* 实现瀑布流布局
*/
function waterFull(parent, child) {
// 1. 父盒子居中
// 1.1 获取所有的盒子
var allBox = $(parent).getElementsByClassName(child);
// 1.2 获取子盒子的宽度
var boxWidth = allBox[0].offsetWidth;
// 1.3 获取屏幕的宽度
var screenW = document.documentElement.clientWidth;
// 1.4 求出列数
var cols = parseInt(screenW / boxWidth);
// 1.5 父盒子居中
$(parent).style.width = cols * boxWidth + 'px';
$(parent).style.margin = "0 auto";
// 2. 子盒子的定位
// 2.1 定义高度数组
var heightArr = [], boxHeight = 0, minBoxHeight = 0, minBoxIndex = 0;
// 2.2 遍历子盒子
for (var i = 0; i < allBox.length; i++) {
// 2.2.1 求出每一个子盒子的高度
boxHeight = allBox[i].offsetHeight;
// 2.2.2 取出第一行盒子的高度放入高度数组
if (i < cols) { // 第一行
heightArr.push(boxHeight);
allBox[i].style = '';
} else { // 剩余行
// 1. 取出最矮的盒子高度
minBoxHeight=Math.min.apply(this,heightArr);
// 2. 求出最矮盒子对应的索引
minBoxIndex = getMinBoxIndex(heightArr, minBoxHeight);
// 3. 子盒子定位
allBox[i].style.position = "absolute";
allBox[i].style.left = minBoxIndex * boxWidth + 'px';
allBox[i].style.top = minBoxHeight + 'px';
// 4. 更新数组中的高度
heightArr[minBoxIndex] += boxHeight;
}
}
// console.log(heightArr, minBoxHeight, minBoxIndex);
}
/**
* 获取数组中最矮盒子高度的索引
* @param arr
* @param val
* @returns {number}
*/
function getMinBoxIndex(arr, val) {
for(var i=0; i<arr.length; i++){
if(arr[i] === val){
return i;
}
}
}
function $(id) {
return typeof id === "string" ? document.getElementById(id) : null;
}
/**
* 判断是否具备加载图片的条件
*/
function checkWillLoadImage() {
// 1. 获取最后一个盒子
var allBox = document.getElementsByClassName("box");
var lastBox = allBox[allBox.length - 1];
// 2. 求出最后一个盒子自身高度的一半 + offsetTop
var lastBoxDis = lastBox.offsetHeight * 0.5 + lastBox.offsetTop;
// 3. 求出屏幕的高度
var screenW = document.body.clientHeight || document.documentElement.clientHeight;
// 4. 求出页面偏离浏览器的高度
var scrollTop = scroll().top;
return lastBoxDis <= screenW + scrollTop;
}
步骤:瀑布流布局封装
传入参数父盒子 子盒子
1.获取所有盒子
2.获取盒子宽度 窗口宽度
3.结合窗口改变 获取列数
4.子盒子定位
5.获取第一行盒子的宽度加入数组 (遍历所有的子盒 子 i小于列数即为第一行 )
6.取出第一行最小值 Math.min.apply(this,数组)
7.添加剩余行的定位 left=最小值的索引*盒子的宽度 top=最小盒子的高度(最小值的索引函数封装实现)
8.更新数组里的最小值 +=当前盒子的高度