数组去重

let ary=[1,2,3,1,1,2,4,5,6]

for (var i = 0; i < ary.length; i++) {
  if (ary.indexOf(ary[i]) != i) {
    ary.splice(i,1);//删除数组元素后数组长度减1后面的元素前移
    i--;//数组下标回退
  }
}
console.log(ary)//[1,2,3,4,5,6]