I'm trying to create an automatic text-to-link conversion feature in a TypeScript application. The desired workflow is:

1. Copy a URL to the clipboard
2. Select some text
3. Paste the URL - this should convert the selected text into a link pointing to the pasted URL

For example:

Selected text: "Click here"
Pasted URL: "https://www.example.com"

Returns: [Click here](https://www.example.com)

This allows easily creating links on the fly without typing Markdown syntax manually.

I tried implementing this in a TypeScript project with the following code:

let selectedText = '';

document.addEventListener('copy', e => {
  const selection = window.getSelection();
  if (selection) {
    selectedText = selection.toString();
  }
});

document.addEventListener('paste', e => {
  if (e.clipboardData) {
    const pasted = e.clipboardData.getData('text');
    if (isValidUrl(pasted)) {
      e.preventDefault();
      insertLink(selectedText, pasted);
    }
  }
});

function insertLink(text: string, url: string): void {
  document.execCommand('insertHTML', false, `[${text}](${url})`);
}

function isValidUrl(url: string): boolean {
  try {
    new URL(url);
    return true;
  } catch (err) {
    return false;
  }
}

To test this code, I set up a TypeScript project on Manjaro Linux and configured Jest for testing:

1. Installed Node.js and npm using sudo pacman -S nodejs npm
2. Created a new TS project

mkdir my-ts-project
cd my-ts-project
npm init -y

3. Installed TypeScript with npm install --save-dev typescript
4. Added a tsconfig.json file with npx tsc --init
5. Installed Jest, ts-jest, and @types/jest packages with npm install --save-dev jest ts-jest @types/jest
6. Added jest.config.js for configuration

module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
};

7. Added test script to package.json
8. Wrote the code in src/index.ts and test cases in src/index.test.ts

// src/index.test.ts

import { Clipboard } from './mocks/clipboard';

describe('copy handler', () => {

  it('copies selected text to clipboard', () => {

    const selectedText = 'hello';

    window.getSelection = () => {
      return {
        toString: () => selectedText  
      } as unknown as Selection;
    };

    document.addEventListener('copy', e => {
      if(e.clipboardData) {
        e.clipboardData.setData('text', selectedText); 
      }
    });

    document.dispatchEvent(new Event('copy'));

    expect(Clipboard.prototype.writeText).toHaveBeenCalledWith(selectedText);
  });

});

describe('paste handler', () => {

  it('inserts link on valid url paste', () => {

    const url = 'https://example.com';
    Clipboard.prototype.clipboardText = url;

    document.addEventListener('paste', e => {
      if(e.clipboardData) {
        const pasted = Clipboard.prototype.readText();
        if(isValidUrl(pasted)) {
          insertLink('text', pasted);
        }
      }
    });

    document.dispatchEvent(new Event('paste'));

    expect(insertLink).toHaveBeenCalledWith('text', url);
  });

});

// src/mocks/clipboard.ts

export class Clipboard {
  public static prototype = {
    writeText: jest.fn(),
    readText: jest.fn(),
    clipboardText: ''
  };
}

9. Ran tests with npm test

However, when running npm test, I got some errors:

> test@1.0.0 test
> jest

 FAIL  src/index.test.ts
  ● Test suite failed to run

    src/index.test.ts:25:32 - error TS2339: Property 'writeText' does not exist on type 'Clipboard'.

    25     expect(Clipboard.prototype.writeText).toHaveBeenCalledWith(selectedText);
                                      ~~~~~~~~~
    src/index.test.ts:35:25 - error TS2339: Property 'clipboardText' does not exist on type 'Clipboard'.

    35     Clipboard.prototype.clipboardText = url;
                               ~~~~~~~~~~~~~
    src/index.test.ts:39:44 - error TS2339: Property 'readText' does not exist on type 'Clipboard'.

    39         const pasted = Clipboard.prototype.readText();
                                                  ~~~~~~~~

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        2.056 s
Ran all test suites.

I want to write tests for:

• empty clipboard
• valid URL
• invalid URL

How can I fix the errors and properly mock the clipboard in the tests?

posted over 1 year ago

CC BY-SA 4.0

1y ago

ShadowsRanger‭

103 reputation 9 1 -9 46