js实现方块的碰撞检测

文章地址：https://www.cnblogs.com/sandraryan/
个人感觉。方块的碰撞检测比圆形麻烦~~
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        body {
            margin: 0;
            padding: 0;
            background-color: lightyellow;
        }

        .wrap {
            width: 50px;
            height: 50px;
            background-color: red;
            position: fixed;
            top: 0;
            left: 0;
        }

        .box {
            position: fixed;
            width: 50px;
            height: 50px;
        }
    </style>
</head>

<body>
    <div class="wrap"></div>
    <div class="box box1">11</div>
    <div class="box box2">22</div>
    <div class="box box3">33</div>
    <div class="box box4">44</div>
    <div class="box box5"></div>
    <div class="box box6"></div>
    <div class="box box7"></div>
    <div class="box box8"></div>
    <div class="box box9"></div>
    <div class="box box10"></div>
    <div class="box box11"></div>
    <div class="box box12"></div>
    <div class="box box13"></div>
    <div class="box box14"></div>
    <div class="box box15"></div>
    <div class="box box16"></div>
    <div class="box box17"></div>
    <div class="box box18"></div>
    <div class="box box19"></div>
    <div class="box box20"></div>
    <script>
        let wrap = document.querySelector('.wrap');
        let box = document.querySelectorAll('.box');
        // 封装随机数函数
        function rn(a, b) {
            return Math.round(Math.random() * (a - b) + b);
        }

        // 循环遍历要被检测的盒子（被检测的盒子也可以用js生成）给他们设置位置和颜色
        for (let i = 0; i < box.length; i++) {
            // 随机生成box的位置
            box[i].style.left = rn(0, 1200) + 'px';
            box[i].style.top = rn(0, 500) + 'px';
            // 设置随机颜色
            let opc = Math.random().toFixed(1);
            // 要用box[i].color接受颜色，本来用变量接受，但是在后面每碰撞成功的元素恢复原有颜色时，所以box都会变成相同的颜色
            box[i].color = 'rgba(' + rn(0, 254) + ',' + rn(0, 254) + ',' + rn(0, 254) + ',' + opc + ')';
            box[i].style.backgroundColor = box[i].color;
        }
        // 文档注册鼠标移动事件
        document.onmousemove = function (ev) {
            let e = ev || window.event;
            // 获取移动盒子的宽高（相等
            // 用变量long接受wrap的宽高，（正方形）
            let long = wrap.offsetWidth;
            // x y 当前窗口宽高-盒子宽高/2
            let x = e.clientX - long / 2;
            let y = e.clientY - long / 2;
            wrap.style.left = x + 'px';
            wrap.style.top = y + 'px';
            // 判断上下左右四个方向是否碰撞
            for (let j = 0; j < box.length; j++) {
                // 顶部：wrap高度 + wrap top值 >= 检测盒子top
                let t = long + wrap.offsetTop >= box[j].offsetTop;
                let b = wrap.offsetTop <= box[j].offsetHeight + box[j].offsetTop;
                let l = long + wrap.offsetLeft >= box[j].offsetLeft;
                let r = wrap.offsetLeft <= box[j].offsetLeft + box[j].offsetWidth;
                // 如果在四个方向任意方向碰撞成功，变色
                if (l && t && r && b) {
                    box[j].style.backgroundColor = 'red';
                } else {
                    box[j].style.backgroundColor = box[j].color;
                }
            }
        }
    </script>
</body>

</html>
js实现方块的碰撞检测

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