Masking eval, extracting FunctionBody – not really sure where it would be used.

mask.js

// Extract FunctionBody as eval expects FunctionBody
Function.prototype.getBody = function() {
  var m = this.toString().match(/\{([\s\S]*)\}/m)[1];
  return m.replace(/^\s*\/\/.*$/mg,'');
};


var GLOBAL = "GLOBAL";

function foo () {
  console.log(GLOBAL, this);
}

function bar () {
  setTimeout(function () {
    console.log(GLOBAL, this);
  }, 0);
}

function hack () {
  console.log(window);
}

foo(); // "GLOBAL"
bar(); // "GLOBAL"

// This function does not restrict access to `window`
function mask (func) {
  "use strict";

  var GLOBAL = 5;
  eval(func.getBody());
}

mask(foo); // 5
mask(bar); // 5