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

There is a function for that, toString, however if you just do console.log(new Test) it will still output the object. But if your force it so print a string it will work: console.log('%s', new Test):

function Test() {
}

Test.prototype.toString =
  function () {
    return "Something else";
  }


console.log("%s", new Test);

> Something else

Or if you concatenate it with another string:

var a = new Test;
console.log('Result: ' + a);

> Result: Something else

I use this a lot in my code to display a summary of the content of a object with data.

There is also valueOf:

Test.prototype.valueOf =
  function () {
    return 42;
  }

console.log("%d", new Test);

> 3