LeetCode Word Search thing

/**
 * @param {character[][]} board
 * @param {string} word
 * @return {boolean}
 */
let currentWord = []  // List of coordinates

function search(board, word, r, c, i) {
    if (i == word.length) // If it finished searching
        return true;
    if (board[r] == undefined || board[r][c] == undefined || board[r][c] != word.substring(i, i + 1) || currentWord.includes(r + " " + c))
        return false;
    currentWord.push(r + " " + c);
    if (search(board, word, r + 1, c, i + 1))
        return true;
    if (search(board, word, r, c + 1, i + 1))
        return true;
    if (search(board, word, r - 1, c, i + 1))
        return true;
    if (search(board, word, r, c - 1, i + 1))
        return true;
    currentWord.pop();
    return false;
};

var exist = function(board, word) {
    currentWord.length = 0 // Why does LeetCode keep the same array throughout all submission trials?? ;-;
    for (let r = 0; r < board.length; r++)
        for (let c = 0; c < board[0].length; c++)
            if (search(board, word, r, c, 0))
                return true;
    return false;
};