javascript - how to get an object to return a value that is not the object itself

Question

When creating a x = new Date() object, if you put it into console.log(x) a string will be output.

Is there a way to make a custom object that w

Answer 1

Overwrite toString of an Object:

My comment above refered to toString as well. You can use JSON.stringify to print out all properties of an object on the fly within an object's toString method:

function MyObject() {
  this.a = 'a';
  this.b = 'b';
  this.c = 'c';
}

MyObject.prototype.toString = function () {
  return JSON.stringify(this);
};

console.log((new MyObject()).toString()); // {"a":"a","b":"b","c":"c"}
// or
console.log('new MyObject(): ' + new MyObject()); // new MyObject(): {"a":"a","b":"b","c":"c"}

Overwrite console.log:

Another try might be to overwrite console.log to print always strings (only tested in FF!):

// initialize this only once so that console.log prints out correctly

(function () {
  var oldConsole = console.log;
  console.log = function (obj) {
    oldConsole(JSON.stringify(obj));
  };
}) ();

// now console.log prints strings
console.log({
  a: 'a'
}); // String: {"a":"a"}

console.log(new Date()); // String: "2017-01-19T19:09:49.673Z"

console.log(document); // String: {"location":{"href":"http://stackoverflow.com/questions/41748793/javascript-how-to-get-an-object-to-return-a-value-that-is-not-the-object-itsel/41749121#41749121","origin":"http://stackoverflow.com","protocol":"http:","host":"stackoverflow.com","hostname":"stackoverflow.com","port":"","pathname":"/questions/41748793/javascript-how-to-get-an-object-to-return-a-value-that-is-not-the-object-itsel/41749121","search":"","hash":"#41749121"},"jQuery112409140067213472354":3}