JavaScript 循环语句 - for 、while 循环

for(var i=0;i<len;i++)
{
    ......
}

var i=0;

while(i<8){
    ......
    i++;
}

var aList = [1,2,3,4,4,3,2,1,2,3,4,5,6,5,5,3,3,4,2,1];

var aList2 = [];

for(var i=0;i<aList.length;i++)
{
    if(aList.indexOf(aList[i])==i)
    {
        aList2.push(aList[i]);
    }
}

alert(aList2);