Using eval on a function string

Question

I am doing :

eval(\'function(){ console.log(\"Hello World\"); }\')();

But that gives error :

Uncaught SyntaxError: Unexpected t         


        

Answer 1

eval expects a statement but:

• function(){} is not valid as a statement because the function name is missing.

• (function(){}) is instead recognized because the statement is a "statement expression".

The problem is that function as first token triggers the function declaration rule when a statement is expected. When an expression is expected instead (e.g. inside parenthesis) then function triggers the function expression rules where a name is optional but not mandatory.