写一个算法找到数组中两个元素相加等于指定数的所有组合

var twoSum = function (nums, target) {  let r1 = (r2 = 0);  for (let o = 0; o < nums.length; o++) {    for (let i = o + 1; i < nums.length; i++) {      if (nums[o] + nums[i] === target) {        r1 = o;        r2 = i;      }    }  }  return [r1, r2];}