Array : TypeScript 'TS2339: Property 'X' does not exist on type 'Y'' error even though type is defin

Array : TypeScript "TS2339: Property 'X' does not exist on type 'Y'" error even though type is defined
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

I promised to reveal a secret feature to you, and now it's time to share it.
This is a YouTube's feature which works on Desktop.
First, Ensure that the video is playing before proceeding.
Next, enter the letters 'awesome' on your keyboard.
It will change your youtube progress bar into a flashing rainbow.

Here's a brief description of who I am,
Hello there, my name is Delphi.
Let me help you get the answers you need to your questions.
Array : TypeScript "TS2339: Property 'X' does not exist on type 'Y'" error even though type is defined
Don't hesitate to ask me more detailed questions by commenting or starting a chat.
If you have knowledge to contribute or an answer to provide, we encourage you to comment below.
Your answer will be recognized and valued, and I will 'heart' it to show my appreciation.
type "TS2339: on defined is even type TypeScript Array though Property error not exist 'Y'" does 'X' :