How to download a chosen DIV with htmltocanvas in javascript image slider?

Html to canvas work but when I click on the download button it only download the first div even if I selected another div in the slider image with the mouse. I would like to select a div with image in the slider with the mouse 1/ select it 2/ Download it.thank you very much in advance for your help. Here is the full code:

var $btn = document.getElementById('btnScreenShot');
$btn.addEventListener('mousedown', onScreenShotClick);

function download( canvas, filename ) {
    // create an "off-screen" anchor tag
    const a = document.createElement('a');

    // the key here is to set the download attribute of the a tag
    a.download = filename;

    // convert canvas content to data-uri for link. When download
    // attribute is set the content pointed to by link will be
    // pushed as "download" in HTML5 capable browsers
    a.href = canvas.toDataURL("image/png;base64");

    a.style.display = 'none';
    document.body.appendChild( a );
    a.click();
    document.body.removeChild( a );
}

function onScreenShotClick(event){
  const element = document.querySelector("#capture");
  
  html2canvas(element).then( ( canvas ) => {
    download( canvas, 'screenshot' );
  });
}

#capture {
  background-color: #b2f5ea;
  padding: 1em;
}

.wp-block-button__link {
    background-color: #0073aa;
    color: #fff;
    transition: background 150ms ease-in-out;
    border: none;
    font-size: 0.88889em;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
    line-height: 1.2;
    box-sizing: border-box;
    font-weight: bold;
    text-decoration: none;
    padding: 0.76rem 1rem;
    outline: none;
    outline: none;
}

img.emoji {
    display: inline !important;
    border: none !important;
    height: 1em !important;
    width: 1em !important;
    margin: 0 .07em !important;
    vertical-align: -0.1em !important;
    background: none !important;
    padding: 0 !important;
    box-shadow: none !important;
}

<script src="http://html2canvas.hertzen.com/dist/html2canvas.js"></script>

<div id="capture">
    <div class="myclass">My image1</div>
</div>
<div id="capture">
    <div class="myclass">My image2</div>
</div>
<div id="capture">
    <div class="myclass">My image3</div>
</div>
<div id="capture">
    <div class="myclass">My image4</div>
</div>

<button type="button" class="btnScreenShot" id="btnScreenShot">Take a Screenshot</button>

<div id="output"></div>

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