Issue: Cannot read property classlist of undefined in web/client sdk

I am getting 3 issues when i am trying to integrate bot with webapp.

  1. A cookie associated with a cross site issue sometimes i comes, & sometime it doesn’t come. How to resolve it permanently?
  2. Uncaught TypeError: Cannot read property ‘classList’ of undefined. This error is coming in the code provided by github. How can i resolve that?
  3. In last input i have provided email id in entity. Bot default language is set as Italian. It should not show this select language here. How can i eliminate this language selection from here?


Please help me to solve these issues
Thanks in advance!

Priyanshu Shukla

I have solved issue 2 & 3 but issue 1 is still open. Please suggest something on that.

Hi Priyanshu,

  1. Can you please elaborate the issue. Please share the frequency of the occurrence.

  2. For the ‘classList’ error, please use the below code at line 676 in ChatWindow.js file to fix the console error.

else if(leftScrollBtn.length){



However, as per our observation, this console error shouldn’t have any impact on the functionality of the bot.

  1. Do you have any default dialog/Welcome message configured for the bot?
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Hi Sadhvi,

Issue 1: It is coming every time when i open it on google chrome.
Issue 2: This error doesn’t affect the bot conversation. Anyways i have resolved that.

Yes there is some welcome message configured for the bot.

Thanks for your help!

Priyanshu Shukla

Hello @priyanshuwwg,

For Issue 1,
It looks like a CORS error, while connecting to the chat window, open the file - SDKApp\routes\users.js

Include the following snippet:

res.header(‘Access-Control-Allow-Origin’, “*”);


var token = jwt.sign(options, clientSecret);




1 Like