javascript – How can I show my magnifying glass only when I hover over the image in CSS?-ThrowExceptions

Exception or error:
// magnify hover
function magnify(imgID, zoom) {
  var img, glass, w, h, bw;
  img = document.getElementById(imgID);
  /*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};
  }
}
/* Initiate Magnify Function
with the id of the image, and the strength of the magnifier glass:*/
magnify("mag", 2);
.img-magnifier-glass {
  position: absolute;
  z-index: 3;
  border: 3px solid #000;
  border-radius: 40%;
  cursor: none;
  /*Set the size of the magnifier glass:*/
  width: 100px;
  height: 100px;
}
<table class="img-magnifier-container" width="115" border="0" cellpadding="0" cellspacing="0" style="display: inline-block"><tr><td width="115" style="text-align: center"><center><a href="https://www.imdb.com/title/tt3315342/" title="Logan 4K (2017)" target="_blank"><img class="cover" width="115" height="133" border="0" id="mag" class="pstrart" id="pstr" src="https://images.static-bluray.com/movies/covers/174423_front.jpg" style=""></a></center><center><input type="checkbox" name="movieboxes" value="Logan" style="width: 15px; height: 15px; margin: 0px;">

Hello,

How can I make the magnifier show only when I hover over the image? I have tried searching on this website and elsewhere, but I don’t understand enough to make the solutions apply to my situation.

I copied this from W3School but they don’t have a section where they explain that I can make it show when I hover over it.

I have modals on my sight and tried to replicate the hovering features of it but it doesn’t seem to work.
Thanks!

How to solve:

Simply toggle opacity on hover:

// magnify hover
function magnify(imgID, zoom) {
  var img, glass, w, h, bw;
  img = document.getElementById(imgID);
  /*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};
  }
}
/* Initiate Magnify Function
with the id of the image, and the strength of the magnifier glass:*/
magnify("mag", 2);
.img-magnifier-glass {
  position: absolute;
  z-index: 3;
  border: 3px solid #000;
  border-radius: 40%;
  cursor: none;
  /*Set the size of the magnifier glass:*/
  width: 100px;
  height: 100px;
  opacity:0;
  pointer-events:none;
}
a:hover .img-magnifier-glass{
  opacity:1;
  pointer-events:initial;
}
<table class="img-magnifier-container" width="115" border="0" cellpadding="0" cellspacing="0" style="display: inline-block"><tr><td width="115" style="text-align: center"><center><a href="https://www.imdb.com/title/tt3315342/" title="Logan 4K (2017)" target="_blank"><img class="cover" width="115" height="133" border="0" id="mag" class="pstrart" id="pstr" src="https://images.static-bluray.com/movies/covers/174423_front.jpg" style=""></a></center><center><input type="checkbox" name="movieboxes" value="Logan" style="width: 15px; height: 15px; margin: 0px;">

###

You can use javascript mouse event handlers. I modified your code snippet below.

What I did is,

.img-magnifier-glass {
  ...
  display:none; // hide the magnifier by default
}
// Show the magnifier when hover the container
$('.img-magnifier-container').mouseover(function(){
  $('.img-magnifier-glass').show();
});

// Hide the magnifier when leave the container
$('.img-magnifier-container').mouseout(function(){
  $('.img-magnifier-glass').hide();
});

// magnify hover
function magnify(imgID, zoom) {
  var img, glass, w, h, bw;
  img = document.getElementById(imgID);
  /*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};
  }
}
/* Initiate Magnify Function
with the id of the image, and the strength of the magnifier glass:*/
magnify("mag", 2);

$('.img-magnifier-container').mouseover(function(){
  $('.img-magnifier-glass').show();
});

$('.img-magnifier-container').mouseout(function(){
  $('.img-magnifier-glass').hide();
});
.img-magnifier-glass {
  position: absolute;
  z-index: 3;
  border: 3px solid #000;
  border-radius: 40%;
  cursor: none;
  /*Set the size of the magnifier glass:*/
  width: 100px;
  height: 100px;
  display:none;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<table class="img-magnifier-container" width="115" border="0" cellpadding="0" cellspacing="0" style="display: inline-block"><tr><td width="115" style="text-align: center"><center><a href="https://www.imdb.com/title/tt3315342/" title="Logan 4K (2017)" target="_blank"><img class="cover" width="115" height="133" border="0" id="mag" class="pstrart" id="pstr" src="https://images.static-bluray.com/movies/covers/174423_front.jpg" style=""></a></center><center><input type="checkbox" name="movieboxes" value="Logan" style="width: 15px; height: 15px; margin: 0px;">

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