原生js实现瀑布流效果

作者: 前端毛毛 | 来源:发表于2018-10-23 13:44 被阅读0次

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

原生js实现瀑布流效果

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