JavaScript drag and drop implementation (with comments), the most classic, simple, short and concise! _javascript skills

Effect preview:
Implementation source code:

<title>Drag[Laugh naturally last modified edit]</title> <div id="r" style="position:absolute; left:100px; top:100px; background-color:#F00; height:80px; width:80px; cursor: pointer;"></div> <div id="g" style="position:absolute; left:250px; top:100px; background-color:#0F0; height:80px; width:80px; cursor: pointer;"></div> <div id="b" style="position:absolute; left:400px; top:100px; background-color:#00F; height:80px; width:80px; cursor: pointer;"></div>
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