螺旋矩阵是指一个呈螺旋状的矩阵，它的数字由第一行开始到右边不断变大，向下变大，向左变大，向上变大，如此循环，接下来用JS实现螺旋矩阵。
核心点是在特殊拐点以及缩短环数处做操作。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<style>
* {
margin: 0;
padding: 0;
}
li {
list-style: none;
}
#ul1 {
margin: 20px auto;
overflow: hidden;
border: 1px #000 solid;
border-right: none;
border-bottom: none;
}
#ul1 li {
float: left;
border: 1px #000 solid;
border-left: none;
border-top: none;
text-align: center;
line-height: 50px;
}
</style>
<body>
<ul id="ul1">
</ul>
</body>
<script >
let oUl = document.getElementById('ul1')
let aLi = document.getElementsByTagName('li')
let sizeGrid = 50
let size = 8
let len = size * size
oUl.style.width = size * (sizeGrid + 1) + 'px'
for (let i = 0; i < len; i++) {
let oLi = document.createElement('li')
oLi.style.width = sizeGrid + 'px'
oLi.style.height = sizeGrid + 'px'
oUl.appendChild(oLi)
}
let row = 0
let col = 0
let min = 0
let max = size - 1
for (let i = 0; i < len; i++) {
aLi[row * size + col].innerHTML = i
if (row == min && col < max) { // 拐点
col = col + 1
} else if (col == max && row < max) { // 拐点
row = row + 1
} else if (row == max && col > min) { // 拐点
col = col - 1
} else if (col == min && row > min) { // 拐点
row = row - 1
}
if (row - 1 == min && col == min) { // 缩短环数
min = min + 1
max = max - 1
}
}
</script>
</html>
