如何给img添加size参数？

<img src="image.jpg" alt="Image" size="500x300">

<style>
    .image {
        width: 500px;
        height: 300px;
        background-image: url("image.jpg");
        background-size: cover;
    }
</style>

<div class="image"></div>

<script>
    var img = document.getElementById("myImage");
    var src = img.getAttribute("src");
    src += "?size=500x300";
    img.setAttribute("src", src);
</script>

<img id="myImage" src="image.jpg" alt="Image">