sub-array-median.js

function findMedian(input1, input2) {
  let resultList = sortLists(input1 || [], input2 || []);
  if (resultList.length > 0) {
    let medianIdx = Math.floor(resultList.length / 2);
    if (resultList.length % 2 === 0) {
      return (resultList[medianIdx - 1] + resultList[medianIdx]) / 2;
    } else {
      return resultList[medianIdx];
    }
  }
}

function sortLists(input1, input2) {
  let result = [];
  let jIdx = 0;

  for (var i = 0; i < input1.length; i++) {
    for (var j = jIdx; j < input2.length && input1[i] > input2[j]; j++) {
      result.push(input2[j]);
      jIdx = j + 1;
    }
    result.push(input1[i]);
  }

  if (jIdx === 0) {
    result = result.concat(input2);
  }
  return result;
}


console.log(findMedian([1, 2], [3, 4]) === 2.5);

console.log(lib.findMedian([1, 5, 9, 10, 15, 20], [2, 3, 8, 13]));