In addition to being obtuse from a syntax perspective, function constructors are also dangerous: their execution evaluates the constructor’s string
arguments similar to the way eval
works, which could expose your program to random, unintended code which can be both slow and a security
risk.
In general it is better to avoid it altogether, particularly when used to parse JSON data. You should use ECMAScript 5’s built-in JSON functions or
a dedicated library.
Noncompliant code example
var obj = new Function("return " + data)(); // Noncompliant
Compliant solution
var obj = JSON.parse(data);
Exceptions
Function calls where the argument is a string literal (e.g. (Function('return this'))()
) are ignored.