JavaScript : Uncaught TypeError: Cannot assign to read only property

JavaScript : Uncaught TypeError: Cannot assign to read only property
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

I have a hidden feature that I promised to tell you about.
This is a YouTube's feature which works on Desktop.
First, Make sure the video is currently in playing mode.
Next, enter the letters 'awesome' on your keyboard.
It will change your youtube progress bar into a flashing rainbow.

A brief introduction of myself,
Hi there, I go by the name of Delphi.
I am here to help you get the answers you are seeking.
JavaScript : Uncaught TypeError: Cannot assign to read only property
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assign : read only TypeError: to property Uncaught JavaScript Cannot