Copy Selected Text in JavaScript

  <script language="javascript">
	/* Source: http://www.apphp.com/index.php?snippet=javascript-copy-selected-text */
    function CopyText(el){
        var selectedText = "";
        if(window.getSelection){
            selectedText = window.getSelection();
        }else if (document.getSelection){
            selectedText = document.getSelection();
        }else if (document.selection){
            selectedText = document.selection.createRange().text;
        }
        if(selectedText != ""){
            selectedText = selectedText.toString();
            el.focus();
            el.value = selectedText;
            }else {
            alert("Select a text in the page and then press this button!");
        }
    }
    </script>
     
    Select any part of this text to copy it...
    <form name="frmCopyText">
    <textarea name="txtSelect" rows="4" cols="45"></textarea><br>
    <input onclick="CopyText(this.form.txtSelect)"
           type="button"
           value="Press to copy the highlighted text"
           name="btnCopy">
    </form>