Server: Sharepoint 2013 On-premise

Client : Windows 7 Pro. + IE 11

Case: We have deployed a Visual Web Part on a 'Web Part Page' in Sharepoint 2013 Server. As soon as client load this page on IE 11 browser it gives "SCRIPT438: Object doesn't support property or method 'startsWith'" JS error in the File "MicrosoftAjaxWebForms.js".

This Visual Web part is working fine on Sharepoint 2007. We are in the process of migration to Sharepoint 2013.

Any Hint to resolve this issue will be much appreciated.



1 Answer 1


The startsWith method is not supported in the following document modes:

  • Quirks
  • Internet Explorer 6 standards
  • Internet Explorer 7 standards
  • Internet Explorer 8 standards
  • Internet Explorer 9 standards
  • Internet Explorer 10 standards
  • Internet Explorer 11 standards.

Not supported in Windows 8.1.

Take a look here.

However, you can use the following snippet in your visual webpart:

<script type="text/javascript">
    if (!String.prototype.startsWith) {
        String.prototype.startsWith = function (searchString, position) {
            position = position || 0;
            return this.indexOf(searchString, position) === position;
  • Thanks Cecilia for your reply. I have added this code already in my web part. But this JS error is coming in MicrosoftAjaxWebForms.js which loads before my web part. so there is any way to modify or load a JS file before MicrosoftAjaxWebForms.js is loaded by sharepoint ?
    – Hafeez
    Jan 17, 2017 at 21:27
  • You are welcome. Check it as correct answer if it was useful.
    – Cecilia
    Jan 17, 2017 at 21:28

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