Using a JSON.parse reviver to obfuscate fields

Question

I am attempting to abuse a reviver function with JSON.parse.

I basically want to make certain fields \"null\".

If I do this:

var json_data = JSON         


        

Answer 1

Through some experimentation, it looks like a final call is made to the function where the key is an empty string and the value is the top-level object:

> JSON.parse('{"hello": "world"}', function(k, v) { console.log(arguments); return v; })
["hello", "world"]
["", Object]

So you could use:

var json_data = JSON.parse(j, function(key, value) {
  if (key == "name" || key === "") {        
    return value;
  } else {
    return null;    
  }    
});

Now, since "" does appear to be a valid JSON key, to be 100% correct it might be better to use something like:

var json_data;
JSON.parse(j, function(key, value) {
  if (key == "name") {        
    return value;
  } else if (key === "") {
    json_data = value;
    return null;
  } else {
    return null;    
  }    
});

But that might be a little bit paranoid ;)