Can not extend String interface

[jkalandarov]

🔎 Search Terms

"typescript does not extend string interface"
"typescript does not augment string interface"
"typescript does not augment global string interface"

🕗 Version & Regression Information

• This is a crash
• This changed between versions ______ and _______
• This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
• I was unable to test this on prior versions because _______

⏯ Playground Link

https://www.typescriptlang.org/play?#code/JYOwLgpgTgZghgYwgAgMpiqA5sg3gKGSOTAHsBhOAWwgBtKBnCACgEoAuZBjbfAX3z50mEFgB0AByikyYAJ4SIYspRr04TNsgC8yGAFcQCMMFIg8hYlAhh9Uc2AAWwBstIAZUgHdojFq0tiYjFrCVpEFgB6ZgB+dgA9AB0vAB8AbQBBAFoALQBdFMSAI2TWSKwAGj1DY1NzZi9SKAATKtBmiAAPVgsgoOtbe2R2rp1tXQAGZBjkRpa3Tx8oPy1OOea3AFUJRWWNfwBuQOQ+AL7g0PCkZkjEhgBqcqqAcmfWI74gA

💻 Code

global.d.ts:

declare global {
  interface String {
    toCamelCase(): string
  }
}

transformers.ts:

interface String {
  toCamelCase(): string
}

String.prototype.toCamelCase = function() {
  return this.toLowerCase()
        .replace(/(?:^\w|[A-Z]|\b\w)/g, function (word, index) {
        return index === 0 ? word.toLowerCase() : word.toUpperCase();
    })
    .replace(/\s+/g, '');
}

actions.ts:

When(/^I click on "([^"]*\sbutton|checkbox|radiobutton)" on "([^"]*)"/, function (element: string, page: string) {
  console.log('**** ', element.toCamelCase()) // <= Returns error
});

🙁 Actual behavior

🙂 Expected behavior

Transform string to camel case

Additional information about the issue

 "devDependencies": {
    "@cucumber/cucumber": "^9.5.1",
    "@playwright/test": "^1.38.0",
    "@types/node": "^20.8.0",
    "multiple-cucumber-html-reporter": "^3.5.0",
    "ts-node": "^10.9.1"
  }

[MartinJohns]

The playground and the code in your issue differ. When you fix the syntactical (JavaScript) errors in your playground it works just fine:

[jkalandarov]

@MartinJohns, it works when I run a single file with ts-node. But when tests start running it fails instantly due to type error as shown in the screenshot.

[jakebailey]

You haven't really posted a working project example (no layout, commands, anything), but if the type works in ts-node but not "cucumber", then there's a misconfiguration that means that d.ts file is not making it into the latter compilation.

[typescript-bot]

This issue has been marked as "External" and has seen no recent activity. It has been automatically closed for house-keeping purposes.