Javascript solution for the Codility Frog River One

FrogRiverOne.js

function solution(X, A) {
    // write your code in JavaScript (Node.js 6.4.0) 

    let sequence = [0];
    let position = -1;
    let counter = 0;

    if (X === 1 && A[0] === 1)
        return 0;

    for (let i = 0; i <= A.length - 1; i++) {

        if (A[i] <= X) {
            if (!sequence[A[i]]) {
                counter++;
            }
            
            sequence[A[i]] = A[i];

            if (counter === X) {
                position = i;
                break;
            }
        }
    }
    return position;
}

function solution(X, A) {

let myNum = 0;
A.sort().map(it =>(it+1) === X+1 ? myNum=it+1 : null)
return myNum;

}
I got 9% : )))) such poor score.