Validity issues

'this' expression which references the global object  

Reports a this expression outside an object literal or a constructor body.

Attempt to assign to const or readonly variable  

Reports reassigning a value to a constant or a readonly variable.

Expression statement which is not assignment or call  

Reports an expression statement that is neither an assignment nor a call.

Function with inconsistent returns  

Reports a function that returns a value in some cases while in other cases no value is returned.

Octal integer  

Reports a deprecated octal integer literal prefixed with 0 instead of 0o.

Reserved word used as name  

Reports a JavaScript reserved word used as a name.

String literal which breaks HTML parsing  

Reports a string literal that contains a </ sequence.