Question

I would want that at passing an object at JSON.Stringify, it checks if it has a field like “val” for stringify only that field, else been stringfied everything.

Is possible to change JSON.Stringify to stringy only a determined field?

Answer 1

It’s quite simple:

function my_json_stringify(obj) {
  return JSON.stringify("val" in obj ? obj.val : obj);
}

console.log(my_json_stringify({ a: 1, b: 2})); // => {"a":1,"b":2}
console.log(my_json_stringify({ val: { a : 3, b: 4 }, other: 5}));
  // => {"a":3,"b":4}

You generally must not modify system functions. It’s very bad idea. But if you have to do it, it can be done like that:

JSON.original_stringify = JSON.stringify;

JSON.stringify = function(obj) {
  return JSON.original_stringify(obj.val ? obj.val : obj);
}

At least, it works in Firefox. But I don’t know if it will work on any other JS implementation or not.