postImage final

 <img id="postImage" alt="Image" class="postimage">
    <script>
        (function () {
            let input = `{TEXT}`
            let id = Date.now()
            $('#postImage').attr('id', id)
            let corsProxy = 'http://cors-proxy.htmldriven.com/?url='
            //let input = `\n[url=https://postimg.cc/image/mk56q648t/][img]https://s14.postimg.cc/mk56q648t/free-steam-key_mini-ninjas.jpg[/img][/url]`
            input = input.replace('\n', '')
            let URL = input.split('][')[0].slice(5)
            let urlProxied = corsProxy + URL
            let pattern = /https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,4}\b([-a-zA-Z0-9@:%_\+.~#?&\/\/=]*)(\.jpg|\.png|\.gif)/

            $.ajax({
                method: 'GET',
                url: urlProxied,
            }).then(function (res) {
                let resString = JSON.stringify(res)
                let matches = resString.match(pattern)[0]
                $(`#${id}`).attr('src', matches).addClass('postimage')
            })
        }())
    </script>