Utilizing a library that solely enhances the functionality of the Array object

Question

Utilizing a library that solely enhances the functionality of the Array object

I have a library with type definitions structured like this:

declare global {
    interface Array<T> {
        addRange<T>(elements: T[]): void;
        aggregate<U>(accumulator: (accum: U, value?: T, index?: number, list?: T[]) => any, initialValue?: U): any;
    }
}

This library is then packaged as an NPM module, but how can I utilize it in another project?

If I attempt to use:

['a', 'b'].addRange(['c', 'd']);

I receive the error message:

Property 'addRange' does not exist on type

Importing just addRange directly won't work because they are extensions of Array.

What is the proper way to import this library so that Typescript recognizes its additions?

angular typescript npm

Answer 1

Answer №1

In the standard practice, you reveal the data types in the npm package's package.json under the types field. When these types comprise global type extensions, they are automatically detected by the compiler once you import the package into the client project.

package.json (library):

{
  "name": "__testPackage",
  "types": "index.d.ts"
  ...
}

index.d.ts (library):

declare global {
  interface Array<T> {
    addRange<T>(elements: T[]): void;
    aggregate<U>(
      accumulator: (accum: U, value?: T, index?: number, list?: T[]) => any,
      initialValue?: U
    ): any;
  }
}

export const foo: number;

app.ts (client):

// If you omit the import statement, Array.prototype.addRange will not be compiled
import { foo } from "__testPackage";

console.log(foo); // Output: 42

const arr = ["a", "b"];
arr.addRange(["c", "d"]); // compiles successfully
console.log(arr); // Output: [ 'a', 'b', 'c', 'd' ]

Answer 2

In the standard practice, you reveal the data types in the npm package's package.json under the types field. When these types comprise global type extensions, they are automatically detected by the compiler once you import the package into the client project.

package.json (library):

{
  "name": "__testPackage",
  "types": "index.d.ts"
  ...
}

index.d.ts (library):

declare global {
  interface Array<T> {
    addRange<T>(elements: T[]): void;
    aggregate<U>(
      accumulator: (accum: U, value?: T, index?: number, list?: T[]) => any,
      initialValue?: U
    ): any;
  }
}

export const foo: number;

app.ts (client):

// If you omit the import statement, Array.prototype.addRange will not be compiled
import { foo } from "__testPackage";

console.log(foo); // Output: 42

const arr = ["a", "b"];
arr.addRange(["c", "d"]); // compiles successfully
console.log(arr); // Output: [ 'a', 'b', 'c', 'd' ]

Answer 3

Answer №2

Develop an anonymous function that appends additional features to the array and wrap it in () for easy calling.

For example:

(function(){
   // Add new methods here
})()

Next, include it in the tsconfig.json or tsconfig.app.json file in Angular 8 under the "files" section

{
  ...
  "files": [
    // Include your extension path here,
    "src/main.ts",
    "src/polyfills.ts"
  ],
  ...
}

Answer 4

Develop an anonymous function that appends additional features to the array and wrap it in () for easy calling.

For example:

(function(){
   // Add new methods here
})()

Next, include it in the tsconfig.json or tsconfig.app.json file in Angular 8 under the "files" section

{
  ...
  "files": [
    // Include your extension path here,
    "src/main.ts",
    "src/polyfills.ts"
  ],
  ...
}

Utilizing a library that solely enhances the functionality of the Array object

Answer №1

Answer №2

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