Count the number of biggest numbers on the board

I coded two answers to this challenge. The first one was a standard attempt, but after it timed out, I figured out the "trick" to solving the problem much more simply. However, I'd still appreciate comments and critiques on my first attempt, because there will be other problems that will need a long approach and I'd like to improve how I'd code the answer.

Challenge
Julia is playing a game on an infinite 2-dimensional grid with the bottom left cell referenced as (1, 1). All the cells contain a value of zero initially. The game consists of n steps. In each step, Julia is given two integers a and b. The value of each of the cells in the coordinate (u, v) satisfying 1 ≤ u ≤ a and 1 ≤ v ≤ b, is increased by 1. After n such steps, if x is the largest number in any cell on the board, how many instances of x are there on the board?

Complete the function countX that has one parameter, a string array, steps, denoting the values of a and b for each of steps of the game. The function should return the total number of occurrences of greatest integer x in the grid after n steps.

Sample Input and Output *

Input: [ '18 29', '32 17', '34 9', '38 15', '36 22', '7 14', '5 100' ]

Output: 2

First Attempt

function countX(stepArr){
    let board = []; //2 dimensional array
    let bigNum = 0;
    let bigNumCount = 0;        

    const stepArrCount = stepArr.length;

     for(let k = 0; k  bigNum){
                        bigNum = board[i][j];
                        bigNumCount = 1;
                    }
                    else if(board[i][j] === bigNum){
                        bigNumCount++;
                    }
                    else{
                        stopCompare = true;
                    }
                }
            }
        }
     }

    return bigNumCount;
}

Second Attempt

```
function countX(stepArr){
let sArr = stepArr[0].split(" ");
let smallColA = parseInt(sArr[0]);
let smallColB = parseInt(sArr[1]);

if(sArr.length > 1){

The second solution

If the input array is empty, the program will crash with an exception.

It's recommended to specify the radix to parseInt calls:

let smallColA = parseInt(sArr[0], 10);

The if(sArr.length > 1){ condition is unnecessary,
the loop condition naturally takes care of that.

Even better, no need to treat the first element specially,
you can initialize smallColA and smallColB to Infinity.
Not only it will be simpler,
but in it will work even when the input array is empty.

The first (naive) solution

You could write this simpler:

if(board[i][j] !== undefined){
    board[i][j]++;
}
else{
    board[i][j] = 1;
}

... using a technique you already used in your other recent question:

board[i][j] = (board[i][j] || 0) + 1;

StackExchange Code Review Q#148920, answer score: 2