Find the first slot to insert a 1D array inside a 2D array

nearestSlotIn2DArray.js

/*
@author @dukuo
​
Sample usage: 
const size_X = 10;
const size_Y = 10;
const sampleArray = new Array(size_X).fill(new Array(size_Y).fill(null));
​
// Fill array with random occurrence of values or null.
for(var j = 0; j < size_Y; j++) {
  const rnd1 = Math.random();
  for(var i = 0; i < size_X; i++) {
    const rnd2 = Math.random();
    if(rnd1 + rnd2 >= .6) {
      sampleArray[i][j] = rnd1;
    } else {
      sampleArray[i][j] = null;
    }
  } 
}
const sampleArrayToInsert = new Array(2);
if(checkNearestEmptySlot(sampleArray, sampleArrayToInsert.length)) {
  console.log("Insertion Logic")
}
*/

const checkNearestEmptySlot = (array, insertLength, filter = null) => {
    const size_X = array[0].length
    const size_Y = array.length
    const err = -1
    let start = err
    let end = err
    for (let j = 0; j < size_Y; j++) {
        for (let i = 0; i < size_X; i++) {
            if (start === err && array[i][j] === filter) {
                start = [i, j]
                // console.log("FOUND A START AT ", start)
            } else if (start !== err && end === err && array[i][j] === filter) {
                end = [i, j]
                // console.log("FOUND AN END AT ", end)
            }
            if (start !== err && end !== err && (Math.abs(start[0] - end[0]) >= insertLength - 1 || Math.abs(start[1] - end[1]) >= 1)) {
                // console.log("FOUND A SLOT TO FIT ", insertLength, " BETWEEN ", start, " AND ", end)
                return start
            }
        }

    }
    return err
}