function(){} vs new Function() vs eval(function(){}) (v12)

Revision 12 of this benchmark created by fbender on

Description

https://developer.mozilla.org/en/JavaScript/Reference/Functions_and_function_scope says

Functions defined by function expressions and function declarations are parsed only once, while those defined by the Function constructor are not. That is, the function body string passed to the Function constructor must be parsed every time it is evaluated. Although a function expression creates a closure every time, the function body is not reparsed, so function expressions are still faster than "new Function(...)". Therefore the Function constructor should be avoided whenever possible.

Which sounds bad.

Changed the code so that the functions are created inside of the test scenario and not the preparation code

Setup

var fn1 = function() {
        return 1 + 2;
        };
    
    var fn2 = new Function('return 1 + 2;');
    
    eval('var fn3 = function(){return 1 + 2;}');
    
    function fn4() {
      return 1 + 2;
    };
    
    var fn5 = function fn5() {
      return 1 + 2;
    }

Test runner

Ready to run.

Testing in
TestOps/sec
Function expression (anonymous fn)
for (var i = 0; i < 10000; i++) {
  fn1();
}
ready
Function constructor
for (var i = 0; i < 10000; i++) {
  fn2();
}
ready
A function created with eval()
for (var i = 0; i < 10000; i++) {
  fn3();
}
ready
Function expression (named fn)
for (var i = 0; i < 10000; i++) {
  fn4();
}
ready
Function expression (named fn + var)
for (var i = 0; i < 10000; i++) {
  fn5();
}
ready

Revisions

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