How override eval function in javascript?

Question

For example:

(function() {
      var proxied = window.eval;
      window.eval = function() {
        return proxied.apply(this, arguments);
      };
    })()         


        

Answer 1

Although not portable, the following approach works in some places where it otherwise wouldn't (as it satisfies ES5's requirements that A) it be retrieved as a Reference in a MemberExpression, not a Value and B) it results in the ‘standard builtin function.’ — ES5 #15.1.2)

(function() {
  var proxied = window.eval
  with({get eval(){ console.log('eval called'); return proxied }}) {
    /* client code */
  }
})()

This obviously only applies if you can wrap the client code in a with() statement; though in many situations, that shouldn't be hard. Obviously, the same approach can shadow window with another object with all of its' properties, and a getter-proxied eval.

Environments that don't support SpiderMonkey's get statement, may be able to use ES5's defineProperty. Look into that yourself.