<form action="">
      <input type="text" class="share-input"  value="http://www.youtube.com" id="copy-content"/>
      <button class="copy-button" type="button" onclick="copyContent();"> 复制 </button>
</form>

<script type="text/javascript">
     /*Copy function implementation */
        function copyContent(){ 
        var copyobject=document.getElementById("copy-content");
        copyobject.select();
        document.execCommand("Copy");
        alert("已复制成功哦~"); 
    };
</script>