Extend a String class in ES6

Question

I can write the following in ES5:

String.prototype.something=function(){
  return this.split(' ').join('');
};

How do I do the same thing in ES6 using the new features?

I know that this is also a valid ES6. I want to know whether there's any other way of implementing such functions in ES6 which is shorter?
The above function is just an example.

Answer 1

In ES6 you can also do it with Object.assign() like this:

Object.assign(String.prototype, {
    something() {
        return this.split(' ').join();
    }
});

You can find more info to the method here .

Or you could use defineProperty (I think that would be better here):

Object.defineProperty(String.prototype, 'something', {
    value() {
        return this.split(' ').join();
    }
});

See the docs here .

See my comment to see when to use defineProperty vs Object.assign() .

Answer 2

Your proposal works fine in ES6, is there something wrong with it?

If you want to actually extend String , instead of just adding a method to String itself, and get that warm ES6 feeling, you could try:

class MyString extends String {
    something() { return this.split(' ').join(''); }
}

However, you are going to quickly run into limitations on extending built-in classes. Chances are you will see the dreaded

TypeError: String.prototype.toString is not generic

error message (this is from babel-node).