Typescript: don't support multiple constructors?

[GerryLon]

TypeScript Version: 2.4.0 / nightly (2.5.0-dev.201xxxxx)

Code

// A *self-contained* demonstration of the problem follows...
class Person {
    private name: string;

    constructor() {

    }

    constructor(name: string) {
        this.name = name;
    }
}

Expected behavior:
compile pass

Actual behavior:
error: Multiple constructor implementations are not allowed.

[ikatyang]

Did you mean constructor overloads?

class Person {
    private name: string;

    constructor();
    constructor(name: string);
    constructor(name?: string) {
        this.name = name;
    }
}

---

Or what you mean is something just like C++ does? See https://github.com/Microsoft/TypeScript/issues/12041#issuecomment-272782978.

[GerryLon]

I mean, Multiple constructor implementations, just like below:

class Person {
    private name: string;

    constructor() {}

    constructor(name: string) {
        this.name = name;
    }
}

as you see, there are two implementations
and I don't understand constructor(); means, how does it work?

[ikatyang]

I think multi-implementations should be duplicate of https://github.com/Microsoft/TypeScript/issues/12041.

EDIT: constructor(); is just a way to show that it can be a 0-param constructor.

EDIT: See TypeScript Docs: Function - Overloads for more about overloads.

[GerryLon]

thank you!

[melodyJie]

I don't know why the constructor can't be more.
It's ok in JAVA or C++

[ikatyang]

Because Javascript itself does not allow, and TS does not want to add more runtime behavior (see TS design goal).