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inherits

function inherits
Jump to headinginherits(
constructor: unknown,
superConstructor: unknown,
): void

Usage of util.inherits() is discouraged. Please use the ES6 class and extends keywords to get language level inheritance support. Also note that the two styles are semantically incompatible.

Inherit the prototype methods from one constructor into another. The prototype of constructor will be set to a new object created from superConstructor.

This mainly adds some input validation on top ofObject.setPrototypeOf(constructor.prototype, superConstructor.prototype). As an additional convenience, superConstructor will be accessible through the constructor.super_ property.

import util from 'node:util';
import EventEmitter from 'node:events';

function MyStream() {
  EventEmitter.call(this);
}

util.inherits(MyStream, EventEmitter);

MyStream.prototype.write = function(data) {
  this.emit('data', data);
};

const stream = new MyStream();

console.log(stream instanceof EventEmitter); // true
console.log(MyStream.super_ === EventEmitter); // true

stream.on('data', (data) => {
  console.log(`Received data: "${data}"`);
});
stream.write('It works!'); // Received data: "It works!"

ES6 example using class and extends:

import EventEmitter from 'node:events';

class MyStream extends EventEmitter {
  write(data) {
    this.emit('data', data);
  }
}

const stream = new MyStream();

stream.on('data', (data) => {
  console.log(`Received data: "${data}"`);
});
stream.write('With ES6');

Parameters Jump to heading

Jump to headingconstructor: unknown
Jump to headingsuperConstructor: unknown

Return Type Jump to heading

void
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