بررسي فعال يا غيرفعال بودن جاواسكريپت

[shirin71]

دستوراتي كه در تگ <script> نوشته ميشند در صورت فعال بودن جاواسكريپت در مرور گر نمايش داده ميشه و دستورات داخل تگ <noscript> در صورت غيرفعال بودن جاوااسكريپت در مرور گر كاربر اجرا ميشند.

نمونه اي از چندمثال:

 
<script type="text/javascript">
    document.write('Only users with JavaScript will see me.');    
</script>
<noscript>
    Only users without JavaScript will see me.
</noscript>

---------

 
<div id="javaScriptOnly" style="display:none">
    Only users with JavaScript will see me.
    <asp:LinkButton runat="server" ... />
</div>
<div id="noJavaScript" style="display:block">
    Only users without JavaScript will see me.
    <asp:Button runat="server" ... />
</div>
<script type="text/javascript">
    document.getElementById('javaScriptOnly').style.display = 'block';
    document.getElementById('noJavaScript').style.display = 'none';
</script>  

البته كنترلي داريم به نام

<inedo:ScriptOnly runat="server">
كه در صورتي كه جاواسكريپت فعال باشه اجرا ميشه.
مثال بالا با استفاده از اين كنترل:

<inedo:ScriptOnly runat="server">
Only users with JavaScript will see me.
<asp:LinkButton runat="server" onClick="doSomething" ... />
</inedo:ScriptOnly>
<noscript>
Only users without JavaScript will see me.
<asp:Button runat="server" onClick="doSomething" ... />
</noscript>

سورس كد كنترلScriptOnly بصورت زيره:

 
[ParseChildren(false)]
public class ScriptOnly : Control
{
    protected override void Render(HtmlTextWriter writer)
    {
        //Render contents to a StringWriter
        StringWriter renderedContents = new StringWriter();
        base.Render(new HtmlTextWriter(renderedContents));

        //write out the contents, line by line
        writer.WriteLine("<script type=\"text/javascript\">");
        StringReader sr = new StringReader(renderedContents.ToString());
        while (sr.Peek() >= 0)
        {
            // This could be optimized to write on one line; but
            // I've found this makes it easier to debug when
            // looking at a page's source
            writer.WriteLine(
                "document.writeln('{0}');",
                jsEscapeText(sr.ReadLine()).Trim());
        }
        writer.WriteLine("</script>");
    }

    private string jsEscapeText(string value)
    {
        if (string.IsNullOrEmpty(value)) return value;

        // This, too, could be optimzied to replace character
        // by character; but this gives you an idea of
        // what to escape out
        return value
            /*  \ --> \\ */
            .Replace("\\", "\\\\")
            /*  ' --> \' */
            .Replace("'", "\\'")
            /*  " --> \" */
            .Replace("\"", "\\\"")
            /*  (newline) --> \n */
            .Replace("\n", "\\n")
            /*  (creturn) --> \r */
            .Replace("\r", "\\r")
            /* </script> string */
            .Replace("</script>", "</scri'+'pt>");
    }
}