The overload feature does not function properly in Angular 2

Trying to overload this method in TypeScript results in it being recognized as a duplicate method. I would like to successfully overload it, though.

    import {Injectable, EventEmitter} from '@angular/core';

@Injectable()
export class NotificationService extends EventEmitter<any>{
    /**
     *
     */
    constructor() {
        super(false);

    }

    public error(message:string ):void{
        this.emit({message: message, type: 'error'});       
    }

    public error(message:string, type:string):void {
        this.emit({message: message, type: type});
    }

    public success(message:string):void{
        this.emit({message: message, type: 'success'})
    }


}

I've attempted some other solutions as well but the issue persists.

  import {Injectable, EventEmitter} from '@angular/core';

@Injectable()
export class NotificationService extends EventEmitter<any>{
    /**
     *
     */
    constructor() {
        super(false);

    }

    public error(message:string, type?:string ):void{
        this.emit({message: message, type: 'error'});       
    }

    public error(message:string, type:string):void {
        this.emit({message: message, type: type});
    }

    public success(message:string):void{
        this.emit({message: message, type: 'success'})
    }


}

The goal is to have it emit an HTTP API response code.

Answer №1

There is no concept of overloading in javascript; since typescript is a superset of javascript, overloading is not supported in typescript either. In Javascript/typescript, object method calls are based on their names.

While overloading may not be necessary in typescript, you can achieve similar functionality by defining optional parameters and default values. For example:

public error(message:string, type?:string):void {
    this.emit({message: message, type: type?type:'error'});
}

Setting a default value for the parameter is another way to simulate overloading (if it was allowed). Additionally, in typescript and es6, you can simplify object property assignments when the variable name matches the property name, like so:

public error(message:string, type:string="error"):void {
    this.emit({message, type});
}

Answer №2

Unlike some other languages, TypeScript and the wider JavaScript community do not natively support method overloading. Instead, you can achieve similar functionality by creating methods that handle optional parameters.

Even though ECMAScript 6 and TypeScript introduced the class keyword, JavaScript's fundamental paradigm remains unchanged. JavaScript is based on prototypes, essentially functioning as a large key-value array. If you define two methods with the same name, the second one will overwrite the first.

Answer №3

It seems like my recent changes are finally starting to work

import {Injectable, EventEmitter} from '@angular/core';

@Injectable()
export class NotificationService extends EventEmitter<any>{
    /**
     *
     */
    constructor() {
        super(true);

    }

    public error(message:string, type?:string):void {
        this.emit({message: message, type: type?type:'error'});
    }

    public success(message:string):void{
        this.emit({message: message, type: 'success'})
    }


}

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