How can i assign javascript variable to vbscript variable - vbscript

Question

How can i assign the text1 value(javascript value) to vbscript variable so that i can write that data into a
text file using ts.WriteLine(av)
I tried submitting the form and getting all the values in the next .asp page and then writing it to a text file,
but my value has many alpha-numeric and special characters....so I cant achieve in that way..any help please.
<% Option Explicit
Const Filename = "/project.txt" ' file to read
Const ForReading = 1, ForWriting = 2, ForAppending = 3
Const TristateUseDefault = -2, TristateTrue = -1, TristateFalse = 0
Dim FSO
set FSO = server.createObject("Scripting.FileSystemObject")
Dim Filepath
Filepath = "E:\applications\FTP\project.txt"
if FSO.FileExists(Filepath) Then
Dim file
set file = FSO.GetFile(Filepath)
Dim TextStream
Set TextStream = file.OpenAsTextStream(ForReading, TristateUseDefault)
%>
<form id="ValidForm" action="">
<input type="textbox" name="ac" id="ac" value="">
<textarea rows="100" cols="230" contenteditable>
<% Do While Not TextStream.AtEndOfStream
Dim Line
Line = TextStream.readline
Line = Line & vbCRLF
Response.write Line
Loop
%>
</textarea>
</form >
<%
Response.Write "</pre><hr>"
Set TextStream = nothing
End If
Set FSO = nothing
%>
<button onclick=abc();>save</button>
<script type="text/javascript" >
function abc()
{alert("1");
var contenteditable = document.querySelector('[contenteditable]'),
text1 = contenteditable.textContent;
//document.getElementById("ac").value=text1;
alert(text1);
}
</script>
<%
'what i should add here to get the javascript variable(text1)
set fs=Server.CreateObject("Scripting.FileSystemObject")
set ts = fs.CreateTextFile("E:\\applications\\FTP\\shivan123.txt",true)
ts.WriteLine("This is my first FileSystemObject application.")
ts.WriteLine( )
ts.Close()
set ts=nothing
set fs=nothing
%>