Move word matching from end-of-path to branching logic

wordSearchImprovement3.js

var exist = function(board, word) {
    var seen = [];
    var targetCharIdx = 0;
    var result = {
        found: false
    };
    for (var i = 0; i < board.length; i++) {
        for (var j = 0; j < board[0].length; j++) {
          if (board[i][j] === word[targetCharIdx]) {
            seen.push([i,j]);
            targetCharIdx++;
            existHelper(board, word, seen, result, targetCharIdx, [i,j])
            targetCharIdx--;
            seen.pop();
          }
        }
    }
    return result.found;
};

var existHelper = function(board, word, seen, result, targetCharIdx, currCell) {
  if (word.length === seen.length) {
    result.found = true;
  }
    var adjCells = adjacentCells(currCell, board);
    for (var i = 0; i < adjCells.length; i++) {
      var adjCell = adjCells[i];
      if (!alreadySeen(adjCell, seen) && isRightChar(adjCell, word[targetCharIdx], board)) {
         seen.push(adjCell);
         existHelper(board, word, seen, result, targetCharIdx + 1, adjCell)
         seen.pop(adjCell)
      }
    }

};


function isRightChar(cell, char, board) {
 return board[cell[0]][cell[1]] === char 
  
}

function adjacentCells(currCell, board) {
 return [[currCell[0] + 1, currCell[1]],
         [currCell[0] - 1, currCell[1]],
         [currCell[0], currCell[1] + 1],
         [currCell[0], currCell[1] - 1]
        ]
      .filter(function(cell) {
          return (cell[0] >= 0 && cell[1] >= 0) &&
                 (cell[0] < board.length && cell[1] < board[0].length)
        });
  
};

function alreadySeen(currCell, seen) {
    var lookup = '';
    var currCell = currCell[0].toString() + currCell[1].toString();
    for (var i = 0; i < seen.length; i++) {
        lookup = seen[i][0].toString() + seen[i][1].toString();
        if (lookup === currCell) {
            return true;
        }
    }
    return false;
}