FibFrog codility JavaScript 100%

function solution(A) {
    
    //other shore bank
    A.push(1);
    
    //array with shortest paths for each leaf/bank
    var reachable = [];
    for(var i = 0; i<A.length; i++){
        reachable.push(-1);
    }
    
    var possibleJumps = fibArray(A.length);

    //get leafs/bank that can be reached from the starting shore
    for(var i = 0; i<possibleJumps.length; i++){
        if(A[possibleJumps[i]-1]===1){
            reachable[possibleJumps[i]-1] = 1;
        }
    }
    
    //for every position not reachable by the first bank find the shortest path
    for(var i = 0; i<A.length; i++){
        if(A[i]===1){
            var minPrevPosition = -1;
            var minDist = A.length+100;
            for(var j = 0; j<possibleJumps.length; j++){
                var prevPosition = i-possibleJumps[j];
                if(prevPosition<0 || reachable[i]>-1){
                    break;
                }
                if(reachable[prevPosition]>0 && minDist>reachable[prevPosition]){
                    minPrevPosition = prevPosition;
                    minDist = reachable[prevPosition];
                }
            }
            if(minPrevPosition > -1){
                reachable[i] = minDist + 1;
            }
        }
    }
    
    return reachable[reachable.length-1];
}

function fibArray(num){
    var current = 2;

    var arr = [0,1,1];

    while(current<=num){
        current++;
        var next = arr[current-1]+arr[current-2];
        arr.push(next);
    }

    return arr;

}