Question

PLEASE DO NOT RECOMMEND JQUERY – I AM DOING THIS EXERCISE FOR LEARNING PURPOSES.

I have implemented a JavaScript, which rotates images (_elementSlideChange) on a timer, using a set interval of 10 seconds. Also I have added a slide functionality to this, which is 7 milliseconds (_slideImage).

The image rotates automatically every 10 seconds on page load, and I have also provided next and previous buttons, which allow the user to change the images manually.

_elementSlideChange: function () {
  var myString;
  var myText;
  for (var i = 0; i < this._imgArray.length; i++) {
    var imageArr = "url(" + this._imgArray[i].src + ")";
    var imageBg = this._imageHolder.style.background + "";
    if (imageArr == imageBg) {
      if (i == (this._imgArray.length - 1)) {
        myString = "url(" + this._imgArray[0].src + ")";
        myText = this._infoArray[0];
      } else {
        myString = "url(" + this._imgArray[(i + 1)].src + ")";
        myText = this._infoArray[i + 1];
      }
    }
  }
  this._imageNextSlide.style.background = myString;
  this._imageNextSlide.style.background);
  this._infoElement.innerHTML = myText;
  this._myTimer = setInterval(MyProject.Utils.createDelegate(this._slideImage, this),  7);
},
_slideImage: function () {
  if (parseInt(this._imageHolder.style.width) >= 0 && parseInt(this._imageNextSlide.style.width) <= 450) {
    this._imageHolder.style.backgroundPosition = "right";
    this._imageHolder.style.width = (parseInt(this._imageHolder.style.width) - 1) + 'px';
    console.log(this._imageNextSlide.style.background);
    this._imageNextSlide.style.width = (parseInt(this._imageNextSlide.style.width) + 1) + 'px';
  } else {
    console.log("reached 0px");
    if (parseInt(this._imageHolder.style.width) == 0) {
      this._imageHolder.style.background = this._imageNextSlide.style.background;
      this._imageHolder.style.width = 450 + 'px';
      this._imageHolder === this._imageNextSlide;
      this._imageHolder.className = "orginalImage";
      this._imageNextSlide.style.width = 0 + "px";
      this._imageNextSlide = this._dummyImageNextSlide;
      this._imagesElement.appendChild(this._imageHolder);
      this._imagesElement.appendChild(this._imageNextSlide);
      clearInterval(this._myTimer);
    }
    clearInterval(this._myTimer);
    clearInterval(this._elementSlideChange);
  }
}

So when the user clicks on the Next arrow button, the event listener for “click” is triggered. This creates a div for the current image on display, and creates a new div, which will contain the next image. The image slide and rotation works correctly (whether it’s onLoad or onClick). The issue I have is if I click the Next button, while the new div image is sliding into position, it causes it to run into an infinite loop, so the same div with the image to be displayed keeps sliding in, and the more you click the Next button, the faster the image starts to rotate.

I have tried putting a clear interval for the image rotation and slider, but I do understand my code is wrong, which causes the infinite loop of the sliding image. And I know I am close to finishing the functionality.

Can anyone please advise where I could be going wrong? Or should I try to implement the sliding DIV in another way?

Once again please don’t recommend jQuery.

And thank you for your help in advance.

Kush

Answer 1

To solve the issue, I did re-write the entire code, where I had a next and previous button event listener.

myProject.Utils.addHandler(this._nextImageElement, "click", myProject.Utils.createDelegate(this._changeImage, this));

Both the buttons will call the same function :

_changeImage: function (e)

In this function I check to see if the function is Transition (changing images),
I declare a boolean var forward = e.target == this._nextImageElement;

Then check to see the current index if forward ? Add 1 else minus 1

this._currentImageIndex += forward ? 1 : -1;

If its at the end of the Array and forward is true, assign the this._currentImageIndex to reset to 0 or Array.length – 1 if it’s in reverse

Then call another function which gives the ‘div’ a sliding effect. In this case call it this._transitionImage(forward);

In this function, set the this._inTranstion to true. (Because the div’s are sliding in this case).

The following code solved the issue i was having.

this._slideImageElement.style.backgroundImage = "url(\"" + this._imgArray[this._currentImageIndex].src + "\")";

this._slideImageElement.style.backgroundPosition = forward ? "left" : "right";        
this._slideImageElement.style.left = forward ? "auto" : "0px";
this._slideImageElement.style.right = forward ? "0px" : "auto";

The above code is very important as the object is to place the “sliding in div” Left or Right of the current Visible “div” to the user, and this is mainly dependent on if the forward variable is true or false.

var i = 0;

Then start the transition by

setInterval( function() {
    this._currentImageElement.style.backgroundPosition = (forward ? -1 : 1) * (i + 1) + "px";
       this._slideImageElement.style.width = (i + 1) + "px";

Notice the forward will determine if the bgPosition will go to the left if its forward as we multiple by -1 or +1,
So for example
If the user clicks NEXT BUTTON,
Forward = true
So the first thing we do is set the

this._slideImageElement.style.backgroundPosition = "left"

Then

this._slideImageElement.style.left = "auto"
this._slideImageElement.style.right = "0px"

This means when the sliding image moves in its background position is LEFT but the div is placed on the RIGHT to 0px;
then this._currentImageElement.style.backgroundPosition = -1 * (i + 1)
Which moves the position of the currentImageElement to the left by 1px,

Increase the width of the slideImage which in this case is right of the current div,
and as the current div moves to the left the sliding image starts to appear from the right. (By default set the width of slideImageElement to 0px so the div exists but isn’t visible to the user). This gives it the slide effect of moving forward new image coming from the right.

this._slideImageElement.style.width = (i + 1) + "px";

then declare it to stop when it it’s the image width. In this case it will be 500px.
if ((i = i + 2) == 500) {
In this if statement reset the currentImageElement background and the background position “right” or “left” don’t really matter as long it has been reset.

Clear the interval
Set the transition to false again
Then call a setTimeout for the function changeImage, which will continue until the slide is completed.

The following shows the reset code as this is very important to prevent repeating the same image (This solved my entire issue)

// set the current image to the "new" current image and reset it's background position
this._currentImageElement.style.backgroundImage = "url(\"" + this._imgArray[this._currentImageIndex].src + "\")";
this._currentImageElement.style.backgroundPosition = "right";

// reset the slide image width
this._slideImageElement.style.width = "0px";

// clear the transition interval and mark as not in transition
clearInterval(this._transitionInterval);
                this._inTransition = false;

// setup the next image timer
this._nextImageTimeout = setTimeout(myProject.Utils.createDelegate(this._changeImage, this), 2500);

}

I have provided a thorough detail because then it easier to understand the logic of the problem, and even if your not having the same issue, this may help you fingure out any problem.

I couldn’t provide a JSfiddle, as i have created my CSS using Javascript, there are different ways of doing this, but i wanted to understand the logic behind the forward and reverse, and having a timer which continuously goes forward.