请问 js 处理这个字符串，怎样写最简洁?

[ljy7723656]

var value = '1,2,3,4,5,6,7,8,9'

输出[2, 5, 8]

输出索引匹配 i%3===1 的整形数组

[cyd]

value.split(",").filter((i,j)=>j%3===1)

[bdbd001]

value.split(",").map((i)=>i*1).filter((i)=>(i%3===2))