leetcode unique paths mxn

uniquepaths.js

/**
 * @param {number} m
 * @param {number} n
 * @return {number}
 */
function uniquePaths(m, n) {
    let arr = [];
    for (let i = 0; i <=m; i++) {
        arr.push(new Array(n + 1).fill(0));
    }
    arr[1][0] = 1;
    for (let i = 1; i <=m; i++){
        for(let j = 1; j<=n; j++){
            arr[i][j] = arr[i - 1][j]+arr[i][j - 1];
        }
    }
    return arr[m][n];
};