如何将自定义 static 方法添加到 TypeScript 中的现有节点 class（例如缓冲区）？

Question

I found a solution to add a method to existing class in TypeScript. I have to declare an interface with the same name and method inside it:

declare interface Buffer {
    foo(): string;
}

Buffer.prototype.foo = function(): string {
    return "bar";
}

But what if I need to add a static method to it ( Buffer.foo , not Buffer.prototype.foo )?

static keyword in declare interface section is not allowed and raises an error: 'static' modifier cannot appear on a type member. ts(1070) 'static' modifier cannot appear on a type member. ts(1070)

UPD:

For @Grey:

You still don't understand what am I looking for. I need a VALID (without //@ts-ignore ) TypeScript implementation of EXACTLY this JavaScript code:

// my-module/index.js

Buffer.foo = function() {
    console.log("bar");
}

to let users do like this:

require("my-module");

Buffer.foo();

The problem is not that I can't find an alternative . The problem is I can do exactly this (↑) in JavaScript but can not in TypeScript. Shouldn't TypeScript be absolutely compatible with JavaScript on the module-structure level at least? I mean, is it normal that I can't implement in TS a module which I can easily implement in JS?

Answer 1

Yes, you can. The idea is the same as you already did before.

Imagine we want to add a static method to Array

You need to:

• Find the declaration for the constructor
• Declare new interface for the constructor with desired method

PoC:

declare interface ArrayConstructor {
    foo(): string;
}

Array.foo = () => `hello from static method`;

Array.foo()

For your case, it will look like

declare interface Uint8ArrayConstructor {
    foo: () => string;
}

Buffer.foo()

PS TSC 3.9.6

Answer 2

SUGGESTION

Following your response: But I want to let users of my module (which is nothing but extension of node's Buffer) call it directly with Buffer.foo

class CustomBuffer extends Buffer {
    public static foo() {
        console.log('I am foo');
    }
}

CustomBuffer.foo(); // I am foo
const buff = CustomBuffer.from('hello world', 'utf8');
console.log(buff); // <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>