Question

Here’s the code I’m working with at the moment:

Object.defineProperty(String.prototype, "testy", {
    get: function() {
        return this.string;
    },
    set: function(string) {
        this.string = string;
    }
});

console.log("tessfef3t".testy());

Before I would’ve used String.prototype.testy = function {}, however I’ve been told that using something similar to the the code above is the better way to do it. I’m not sure how that is meant to work but I haven’t got that code to work yet.

Could someone show me how to correctly do what I’m doing?

Thanks

Answer 1

testy is kind of a “fake” property — it has no value of its own, but setting or getting its value will invoke its set and get functions. You can use it like:

var foo = new String();

// this invokes the setter and sets foo.string to 5:
foo.testy = 5; 

// this invokes the getter and prints the value of foo.string
console.log(foo.testy); 

// this prints 5, because foo.string has been set by the setter
console.log(foo.string);

EDIT:

Now I see your comment about what you actually want to happen. It’s not possible to alter the value of a string object, because strings are immutable. You’d have to destroy the string object and replace it with a new one, which is not possible within the object’s own member function.