window.onload = function () {
        var lis = document.getElementsByTagName('li');
        lis[0].style.backgroundColor = 'gold';
        lis[1].style.backgroundColor = 'gold';
    }

document.getElementsByTagName();標(biāo)簽獲取元素

循環(huán)

1.for循環(huán)

 window.onload = function () {
        var olist = document.getElementById('list01');
        var ali = olist.getElementsByTagName('li');

         for(var i=0;i<8;i++){
            if(i%2 == 0){
              ali[i].style.backgroundColor = 'gold';
            }
        }
        i++;
    }

2.while循環(huán)

 var i=0;
 while (i<ali.length){
      if(i%2 == 0){
          ali[i].style.backgroundColor = 'gold';
                 }
           }
           i++;
           };

3.do while循環(huán)

var i = 0;
        do {
            if (i % 2 == 0) {
                ali[i].style.backgroundColor = 'gold';
            }
            i++;
        } while (i < ali.length);
    }

while和do while的區(qū)別:
do while是大括號(hào)里無(wú)論如何都先執(zhí)行一次，執(zhí)行完再判斷是否成立
while是先判斷是否成立，然后在執(zhí)行大括號(hào)的內(nèi)容