What is the meaning of this operator("?:") in javascript- question mark and colon

method?: string | undefined;

what is the meaning of this line in javascript

I tried interpreting it as a conditional operator with null assigned to the method in case it has true boolean value
But this is not correct

>Solution :

It’s not JavaScript, it’s TypeScript (probably). It’s not a single operator, it’s:

• The ? marker indicating that the property or function parameter is optional (optional properties, optional parameters)
• The : that starts the beginning of a type annotation