myImgSrc = "";
myImgEnd = "";
var i = 0;

// Create function to load image
function loadImg(){
  document.getElementById('counter').innerHTML = '1';
  document.getElementById('imgSrc').src = myImgSrc + myImg[i] + myImgEnd;
}

// Create link function to switch image fborward
function show(a){
  i = a;
  document.getElementById('counter').innerHTML = i+1;
  document.getElementById('imgSrc').src = myImgSrc + myImg[i] + myImgEnd;
}

// Create link function to switch image backward
function prev(){
  if(i<1){
    var l = i
  } else {
    var l = i-=1;
  }
  document.getElementById('counter').innerHTML = l+1;
  document.getElementById('imgSrc').src = myImgSrc + myImg[l] + myImgEnd;
}

// Create link function to switch image forward
function next(){
  if(i>myImg.length-2){
    var l = i
  } else {
    var l = i+=1;
  }
  document.getElementById('counter').innerHTML = l+1;
  document.getElementById('imgSrc').src = myImgSrc + myImg[l] + myImgEnd;
}

// Load function after page loads
loadImg();