简单的方法是像这样

var functionPool = {} // create a variable to hold the original versions of the functions

for( var func in window ) // scan all items in window scope
{
  if (typeof(window[func]) === 'function') // if item is a function
  {
    functionPool[func] = window[func]; // store the original to our global pool
    (function(){ // create an closure to maintain function name
         var functionName = func;
         window[functionName] = function(){ // overwrite the function with our own version
         var args = [].splice.call(arguments,0); // convert arguments to array
         // do the logging before callling the method
         console.log('logging: ' + functionName + '('+args.join(',')+')');
         // call the original method but in the window scope, and return the results
         return functionPool[functionName].apply(window, args );
         // additional logging could take place here if we stored the return value ..
        }
      })();
  }
}

要解开你需要运行

for (func in functionPool)
  window[func] = functionPool[func];

注释

仅处理全局函数，但你可以很容易地扩展它来处理特定的对象或方法等。

Notes
This handles only global functions, but you can easily extend it to handle specific objects or methods etc..