Смена картинки при клике на ссылку

<script type="text/javascript"> 
    var index = 0;
    var links = new Array (
        "/assets/templates/Sky/img/plus.png",  
    "/assets/templates/Sky/img/minus.png"
    ); 
  
    function slide(v) {
        var element = document.getElementById("pic1");
        index += 1 * v;
            
        if(index > links.length - 1) index = 0;
        else if(index < 0) index = links.length - 1;
        element.src = links[index];
  }  
</script>

<script type="text/javascript"> 
    var index = 0;
    var index1 = 0;
    var links = new Array (
        "/assets/templates/Sky/img/plus.png",  
        "/assets/templates/Sky/img/minus.png"
    );
    
function slide(myid,v) {
    var element = document.getElementById(myid);
 
    if(myid=="pic"){  
        index += v;
        if(index > links.length - 1) index = 0;
        else if(index < 0) index = links.length - 1;
        element.src = links[index];
    }
    
    if(myid=="pic1"){
        index1 += v;
        if(index1 > links.length - 1) index1 = 0;
        else if(index1 < 0) index1 = links.length - 1;
        element.src = links[index1];
    }
}  
</script>

var links = [
  "http://lorempixel.com/40/40",  
  "http://lorempixel.com/40/41"
];
 
var spoilerLink = document.getElementsByClassName("spoiler_links");
 
for (var i = 0, count = spoilerLink.length; i < count; i++) {
  spoilerLink[i].onclick = function() {
    if (this.previousElementSibling.src === links[0]) {
      this.previousElementSibling.src = links[1];
    } else {
      this.previousElementSibling.src = links[0];
    }
    return false;
  }
}