The reason for my inability to include a fresh method in String.prototype using typescript

Question

The reason for my inability to include a fresh method in String.prototype using typescript

I attempted to extend the String.prototype with a new method, but I encountered an issue.

interface String {
  newMethod(): void
}

String.prototype.newMethod = function() {}

Although there were no errors in the typescriptlang.org playground, I received the error message

Property 'newMethod' does not exist on type 'String'

when testing it on my local computer.

I am puzzled by this inconsistency.

Below is an excerpt from my tsconfig.json

{
  "compilerOptions": {
    "target": "es2015",
    "module": "commonjs",
     "outDir": "./lib",
     "rootDir": "./src",
  }
}

I also made sure to install `@types/node

Upon further research, I came across some interesting examples.

// example1: no error
interface String {
  newMethod(): void
}

String.prototype.newMethod = function() {}

// example2: has error
import * as path from 'path'
interface String {
  newMethod(): void
}

String.prototype.newMethod = function() {}

The addition of only an import statement seemed to trigger the error. This behavior is quite baffling to me. Any insights?

javascript typescript

Answer 1

Answer №1

I recently created a custom "replaceAll" function in JavaScript...

export {};

declare global {
    // Defining a new method for String interface
    interface String {
        replaceAll(searchFor: string, replaceWith: string): string;
    }
}

// Overriding the existing replace method to enable replacing all occurrences
String.prototype.replaceAll = function(this: string, searchFor: string, replaceWith: string) {
    var value = this; // Storing the original string
    var index: number = value.indexOf(searchFor); // Finding index of search term

    // Replacing all occurrences within the string
    while (index > -1) {
        value = value.replace(searchFor, replaceWith);
        index = value.indexOf(searchFor);
    }

    return value; // Returning the modified string
};

Answer 2

I recently created a custom "replaceAll" function in JavaScript...

export {};

declare global {
    // Defining a new method for String interface
    interface String {
        replaceAll(searchFor: string, replaceWith: string): string;
    }
}

// Overriding the existing replace method to enable replacing all occurrences
String.prototype.replaceAll = function(this: string, searchFor: string, replaceWith: string) {
    var value = this; // Storing the original string
    var index: number = value.indexOf(searchFor); // Finding index of search term

    // Replacing all occurrences within the string
    while (index > -1) {
        value = value.replace(searchFor, replaceWith);
        index = value.indexOf(searchFor);
    }

    return value; // Returning the modified string
};

The reason for my inability to include a fresh method in String.prototype using typescript

Answer №1

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