Interface = Obligation.
To implement an interface = Provide members which are expected by these who call you.
What the docs say about this particular interface, the ReadableStream?
Well, here it says
All Readable streams implement the interface defined by the stream.Readable class
And what is the stream.Readable?
Well, here a complete "interface" is provided and it consists of multiple members, including read, pipe and others.
Technically, in JS there are multiple ways of "implementing" such obligation:
an easy way is to set an object that already implements the interface in the prototype chain of an object that is supposed to implement the interface. This way all interface members are delegated (by means of the proto chain) to the other object
a more direct way is just to provide all necessary members directly by the object that is supposed to implement the interface
a hybrid approach where some members are delegated down the proto chain, some members are implemented directly and some members are delegated to other objects by direct invocation
Because of the nature of the language, the caller which expect the interface to be implemented will accept all these possibilities.
E.g. The docs says the interface contains a method
foo(n)
where n is a number
returns a number
You have following options.
Option 1, a direct implementation
var o = {
foo: function(n) {
return 0;
}
}
Option 2, delegation down the proto chain
// an object that already implements the interface
// i.e. has function foo(n)
var existing = ....;
var o = Object.create(existing);
// o has function foo though its proto
Option 3, delegation by invocation
// an object that already implements the interface
// i.e. has function foo(n)
var existing = ....;
var o = {
foo: function(n) {
return existing(n);
}
}
All these options can possibly be expressed with construction functions, too.
