Change the value of the formenctype attribute of a submit button to "application/x-www-form-urlencoded":
document.getElementById("mySubmit").formEnctype = "application/x-www-form-urlencoded";
<!DOCTYPE html> <html> <body> <form action="/action_page_binary.asp" method="post"> Name: <input type="text" name="fname" value="css"><br> <input type="submit" id="mySubmit" formenctype="text/plain" value="Submit"> </form>// ww w .j a va2 s . com <button onclick="myFunction()">Test</button> <p id="demo"></p> <script> function myFunction() { document.getElementById("mySubmit").formEnctype = "application/x-www-form-urlencoded"; document.getElementById("demo").innerHTML = "The value of the formenctype attribute was changed from 'text/plain' to 'application/x-www-form-urlencoded'."; } </script> </body> </html>