Looping through an object and changing all values

try

var superSecret = function(spy){
  Object.keys(spy).forEach(function(key){ spy[key] = "redacted" });
  return spy;
}

You can also go functional.

Using Object.keys is better as you will only go through the object properties and not it's prototype chain.

Object.keys(spy).reduce((acc, key) => {acc[key] = 'redacted'; return acc; }, {})

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