所以CSV是字符串90,90,90,90,90 3,1,1000,2,931
让我们将字符串转换为int数组

const arr = csv.split(",").map(e => parseInt(e));

查找元素=== 2的索引将是

const index = arr.findIndex(e => e === 2);
console.log(index); // 7

更改其值

arr[index] = 3; // Its value will now be 3
console.log(arr); // [ 90, 90, 90,90, 90, 1,1000, 3, 931 ]

现在，我们根据新修改的值重新分配变量“csv

csv = arr.join(",")
console.log(csv) // '90,90,90,90,90,1,1000,3,931'