How to dynamically incorporate methods into a TypeScript class

Question

How to dynamically incorporate methods into a TypeScript class

I'm currently attempting to dynamically inject a method into an external class in TypeScript, but I'm encountering the following error.

Error TS2339: Property 'modifyLogger' does not exist on type 'extclass'.

Here's the code snippet:


    extclass['modifyLogger'] = function(mylogger:any){

     }

    interface extclass{
        modifyLogger(): void;
     }


     let obj = new extclass();
      obj.modifyLogger(log);

The above code is resulting in an error message.

Can anyone identify what I might be overlooking here?

typescript

Answer 1

Answer №1

It is recommended to utilize the following:

extclass.prototype['modifyLogger'] = function(mylogger:any){ }

instead of the code provided previously.

Furthermore, please ensure to correct the declaration of 'modifyLogger()' in the interface to accept a parameter.

interface extclass{
    modifyLogger(arg: any): void;
}

Update Kindly refer to the updated TS Playground

class Extclass { 
    test() {

    }
}

interface Extclass {
    modifyLogger(): void;
}

class Test {
    constructor() { 
        Extclass.prototype['modifyLogger'] = function () {
            alert('hi');
        }
        var obj = new Extclass();
        obj.modifyLogger();
    }
}

var t = new Test();

Answer 2

It is recommended to utilize the following:

extclass.prototype['modifyLogger'] = function(mylogger:any){ }

instead of the code provided previously.

Furthermore, please ensure to correct the declaration of 'modifyLogger()' in the interface to accept a parameter.

interface extclass{
    modifyLogger(arg: any): void;
}

Update Kindly refer to the updated TS Playground

class Extclass { 
    test() {

    }
}

interface Extclass {
    modifyLogger(): void;
}

class Test {
    constructor() { 
        Extclass.prototype['modifyLogger'] = function () {
            alert('hi');
        }
        var obj = new Extclass();
        obj.modifyLogger();
    }
}

var t = new Test();

How to dynamically incorporate methods into a TypeScript class

Answer №1

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