Image zoom on multiple images

Question

I've used a pretty standard image zoom effect from the following example: https://www.w3schools.com/howto/howto_js_image_magnifier_glass.asp

The HTML + CSS + JS is pretty much exactly what is used in the example above.

This works perfectly on 1 image. However when multiple images are used it only works on the first image.

I'm pretty sure it's to do with using getElementById instead of querySelectorAll for some things (possibly var img and var result) hence why it's only applying to the first instance of #myimage.

Can anyone help me run this code but loop it over ALL images (with #myimage as the ID)?

Much appreciated!

Original code below:

JAVASCRIPT:
// enable image zoom

function imageZoom(imgID, resultID) {
  var img, lens, result, cx, cy;
  img = document.getElementById(imgID);
  result = document.getElementById(resultID);
  
  
  /* Create lens: */
  lens = document.createElement("DIV");
  lens.setAttribute("class", "img-zoom-lens");
  
  
  /* Insert lens: */
  img.parentElement.insertBefore(lens, img);
  
  
  
  
  /* Calculate the ratio between result DIV and lens: */
  cx = result.offsetWidth / lens.offsetWidth;
  cy = result.offsetHeight / lens.offsetHeight;
  /* Set background properties for the result DIV */
  result.style.backgroundImage = "url('" + img.src + "')";
  result.style.backgroundSize = (img.width * cx) + "px " + (img.height * cy) + "px";
  /* Execute a function when someone moves the cursor over the image, or the lens: */
  lens.addEventListener("mousemove", moveLens);
  img.addEventListener("mousemove", moveLens);
  /* And also for touch screens: */
  lens.addEventListener("touchmove", moveLens);
  img.addEventListener("touchmove", moveLens);
  function moveLens(e) {
    var pos, x, y;
    /* Prevent any other actions that may occur when moving over the image */
    e.preventDefault();
    /* Get the cursor's x and y positions: */
    pos = getCursorPos(e);
    /* Calculate the position of the lens: */
    x = pos.x - (lens.offsetWidth / 2);
    y = pos.y - (lens.offsetHeight / 2);
    /* Prevent the lens from being positioned outside the image: */
    if (x > img.width - lens.offsetWidth) {x = img.width - lens.offsetWidth;}
    if (x < 0) {x = 0;}
    if (y > img.height - lens.offsetHeight) {y = img.height - lens.offsetHeight;}
    if (y < 0) {y = 0;}
    /* Set the position of the lens: */
    lens.style.left = x + "px";
    lens.style.top = y + "px";
    /* Display what the lens "sees": */
    result.style.backgroundPosition = "-" + (x * cx) + "px -" + (y * cy) + "px";
  }
  function getCursorPos(e) {
    var a, x = 0, y = 0;
    e = e || window.event;
    /* Get the x and y positions of the image: */
    a = img.getBoundingClientRect();
    /* Calculate the cursor's x and y coordinates, relative to the image: */
    x = e.pageX - a.left;
    y = e.pageY - a.top;
    /* Consider any page scrolling: */
    x = x - window.pageXOffset;
    y = y - window.pageYOffset;
    return {x : x, y : y};
  }
}


imageZoom("myimage", "myresult");

HTML:
<img src='https://via.placeholder.com/250' id="myimage">

<div id="myresult" class="img-zoom-result"></div>

Answer 1

Something like this?

function magnify(img, zoom) {
   var glass, w, h, bw;
  /* Create magnifier glass: */
  glass = document.createElement("DIV");
  glass.setAttribute("class", "img-magnifier-glass");

  /* Insert magnifier glass: */
  img.parentElement.insertBefore(glass, img);

  /* Set background properties for the magnifier glass: */
  glass.style.backgroundImage = "url('" + img.src + "')";
  glass.style.backgroundRepeat = "no-repeat";
  glass.style.backgroundSize = (img.width * zoom) + "px " + (img.height * zoom) + "px";
  bw = 3;
  w = glass.offsetWidth / 2;
  h = glass.offsetHeight / 2;

  /* Execute a function when someone moves the magnifier glass over the image: */
  glass.addEventListener("mousemove", moveMagnifier);
  img.addEventListener("mousemove", moveMagnifier);

  /*and also for touch screens:*/
  glass.addEventListener("touchmove", moveMagnifier);
  img.addEventListener("touchmove", moveMagnifier);
  function moveMagnifier(e) {
    var pos, x, y;
    /* Prevent any other actions that may occur when moving over the image */
    e.preventDefault();
    /* Get the cursor's x and y positions: */
    pos = getCursorPos(e);
    x = pos.x;
    y = pos.y;
    /* Prevent the magnifier glass from being positioned outside the image: */
    if (x > img.width - (w / zoom)) {x = img.width - (w / zoom);}
    if (x < w / zoom) {x = w / zoom;}
    if (y > img.height - (h / zoom)) {y = img.height - (h / zoom);}
    if (y < h / zoom) {y = h / zoom;}
    /* Set the position of the magnifier glass: */
    glass.style.left = (x - w) + "px";
    glass.style.top = (y - h) + "px";
    /* Display what the magnifier glass "sees": */
    glass.style.backgroundPosition = "-" + ((x * zoom) - w + bw) + "px -" + ((y * zoom) - h + bw) + "px";
  }

  function getCursorPos(e) {
    var a, x = 0, y = 0;
    e = e || window.event;
    /* Get the x and y positions of the image: */
    a = img.getBoundingClientRect();
    /* Calculate the cursor's x and y coordinates, relative to the image: */
    x = e.pageX - a.left;
    y = e.pageY - a.top;
    /* Consider any page scrolling: */
    x = x - window.pageXOffset;
    y = y - window.pageYOffset;
    return {x : x, y : y};
  }
}
[…document.querySelectorAll(“#myimage”)].forEach( img => {
 magnify(img,3);
})