找工作时的面试题，使用*打印出菱形，忽然没有什么思路，翻了翻百度上别个写的，自己实现出了一种方法。
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<html lang="en">
<head>
<meta charset="UTF-8">
<meta
http-equiv="X-UA-Compatible"
content="IE=edge"
>
<meta
name="viewport"
content="width=device-width, initial-scale=1.0"
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<title>使用 * 打印出菱形</title>
</head>
<body>
<script>
let num = 7;
function fn (num) {
let n = Math.ceil(num / 2);
for (let i = 0; i < n; i++) {
for (let j = 0; j < n - i; j++) {
document.write(" ");
}
for (let j = 0; j < 2 * i + 1; j++) {
document.write(" * ");
}
document.write("<br/>");
}
for (let i = 1; i <= num - n; i++) {
for (let j = 0; j <= i; j++) {
document.write(" ");
}
for (let k = 1; k <= num - 2 * i; k++) {
document.write(" * ");
}
document.write("<br/>");
}
}
fn(num)
</script>
</body>
</html>