Tracker for conversation id

I am new to rasa and I pick up a rasa chatbot developed from the senior. So I have problem for tracker for conversation ID.

In the javascript from senior, he had hardcode the user_id=“kiew”. So it will having a error message “Conversation ID not found.” when I run the chatbot.

In the webpage, it will also having a error message , but it also can still respond when a message is typed. For example

The code of error message:

Can anyone help me to solve this problem…?

The string inside the red box should be inside backticks ` and not apostrophes ’ to properly convert the variable:

var name= 'Chris'
console.log('I am ${name}') // -> I am ${name}
console.log(`I am ${name}`) // -> I am Chris