JS实现九九乘法表（for双重循环的典型例子）

  <script>
        var str = " ";
        for (var i = 1; i <= 9; i++) {
            for (var j = 1; j <= i; j++) {
                str += j + "x" + i + "=" + i * j + "\t";
            }
            str += "\n"
        }
        console.log(str);
    </script>