Test

<div id="url-image-search">
        <strong>Paste Image link URL</strong><br><br>
        <input type="url" id="img_url" name="img_url" maxlength="999" placeholder="https://...  .jpg .png"><br><br>
        <a onclick="searchImage('https://lens.google.com/uploadbyurl?url=')" class="btn" style="background-color: #1A6EE1; color:#fff;">Google</a>
        <a onclick="searchImage('https://yandex.com/images/search?url=')" class="btn" style="background-color: #DE2520; color:#fff;">Yandex</a>
        <a onclick="searchImage('https://www.bing.com/images/search?q=imgurl:')" class="btn" style="background-color: #027F6E; color:#fff;">Bing</a>
    </div>

    <script type="text/javascript">
        function searchImage(baseURL) {
            var img_url = document.getElementById('img_url').value;
            if (!img_url || !isValidHttpUrl(img_url)) {
                alert('Please enter a valid image URL.');
                return;
            }
            window.open(baseURL + encodeURIComponent(img_url) + (baseURL.includes('yandex') ? "&rpt=imageview" : baseURL.includes('bing') ? "&view=detailv2&iss=sbi" : ''));
        }

        function isValidHttpUrl(string) {
            let url;
            try {
                url = new URL(string);
            } catch (_) {
                return false;  
            }
            return url.protocol === "http:" || url.protocol === "https:";
        }
    </script>