<!DOCTYPE html>
<html>

  <head>
    <meta charset="UTF-8">
    <title></title>
  </head>

  <body>
    <script type="text/javascript">
      for(var i = 0; i < 10; i++) {
        for(var j = 0; j < i; j++) {
          document.write("*");
        }
        document.write("<br/>");
      }

      var m = 0;
      var result = 0;
      while(m <= 100) {
        result += m;
        m++;
      }

      document.write("0+1+2...+100 = " + result);
      document.write("<hr>");

      //for in 
      //定义数组
      var arr = new Array();
      //赋值
      arr[0] = 10;
      arr[1] = 100;
      arr[2] = 1000;
      arr[3] = 10000;
      //使用for ... in 遍历
      //for(变量 in 数组) 
      //每次循环，都取出数组的下标
      for(var num in arr) {
        document.write(arr[num]);
        document.write("<br/>");
      }
    </script>
  </body>

</html>