综合案例

案例1：求质数

    var n = 18
    for (var i = 2; i <= n/2; i++) {
        if (n % i === 0) {
            console.log(n + '不是质数')
            break
        }
    }
    if (!(i<=n/2)){
        console.log(n + '是质数')
    }

案例2：九九乘法表

    <style>
        span{
            display: inline-block;
            width: 80px;
            height: 20px;
            line-height: 20px;
            text-align: center;
            border: 1px solid #000;
        }
    </style>
    for (var i = 1; i <= 9; i++) {
        for (var j = 1; j <= i; j++) {
            document.write('<span>'+j + '*' + i + '=' + i * j + '</span>')
        }
        document.write('<br>')
    }