Discover the versatility of TypeScript by dynamically adding methods to a class!

Question

Discover the versatility of TypeScript by dynamically adding methods to a class!

Are there any examples of dynamically extending a class with a method in TypeScript? I attempted the following:

UsersBlocksMyOrders.prototype.myFunc = function():any{
  alert('23434');
};

However, the compiler is giving me an error.

javascript typescript inheritance prototype

Answer 1

Answer №1

Typically, you would need to follow a pattern similar to this:

interface UsersBlocksMyOrders {
    myFunc(): any;
}

If not, the compiler won't recognize it.

This concept also applies to existing classes. For instance:

interface String {
    logit(): void;
}

String.prototype.logit = function () {
    console.log(this);
}

let a = "string";
a.logit();

(Code snippet in playground)

In cases where you need to modify another module, known as Module Augmentation, you should do something like this:

Import { UsersBlocksMyOrders } from "../pages/users/blocks/myorders";

declare module "../pages/users/blocks/myorders" {
    interface UsersBlocksMyOrders {
        logit(): void;
    }
}

UsersBlocksMyOrders.prototype.logit = function () { console.log(this); }

If feasible (which appears to be the case here), directly modifying the source code is preferable. Resort to this method only when necessary.

Answer 2

Typically, you would need to follow a pattern similar to this:

interface UsersBlocksMyOrders {
    myFunc(): any;
}

If not, the compiler won't recognize it.

This concept also applies to existing classes. For instance:

interface String {
    logit(): void;
}

String.prototype.logit = function () {
    console.log(this);
}

let a = "string";
a.logit();

(Code snippet in playground)

In cases where you need to modify another module, known as Module Augmentation, you should do something like this:

Import { UsersBlocksMyOrders } from "../pages/users/blocks/myorders";

declare module "../pages/users/blocks/myorders" {
    interface UsersBlocksMyOrders {
        logit(): void;
    }
}

UsersBlocksMyOrders.prototype.logit = function () { console.log(this); }

If feasible (which appears to be the case here), directly modifying the source code is preferable. Resort to this method only when necessary.

Answer 3

Answer №2

This code snippet can be found at this link:

function combineObjects<T, U>(first: T, second: U): T & U {
    let result = <T & U>{};
    for (let key in first) {
        (<any>result)[key] = (<any>first)[key];
    }
    for (let key in second) {
        if (!result.hasOwnProperty(key)) {
            (<any>result)[key] = (<any>second)[key];
        }
    }
    return result;
}

class Person {
    constructor(public name: string) { }
}
interface Loggable {
    log(): void;
}
class ConsoleLogger implements Loggable {
    log() {
        // ...
    }
}
var jim = combineObjects(new Person("Jim"), new ConsoleLogger());
var n = jim.name;
jim.log();

Answer 4

This code snippet can be found at this link:

function combineObjects<T, U>(first: T, second: U): T & U {
    let result = <T & U>{};
    for (let key in first) {
        (<any>result)[key] = (<any>first)[key];
    }
    for (let key in second) {
        if (!result.hasOwnProperty(key)) {
            (<any>result)[key] = (<any>second)[key];
        }
    }
    return result;
}

class Person {
    constructor(public name: string) { }
}
interface Loggable {
    log(): void;
}
class ConsoleLogger implements Loggable {
    log() {
        // ...
    }
}
var jim = combineObjects(new Person("Jim"), new ConsoleLogger());
var n = jim.name;
jim.log();

Discover the versatility of TypeScript by dynamically adding methods to a class!

Answer №1

Answer №2

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