How can we incorporate methods using TypeScript?

I'm currently diving into TypeScript and encountering some challenges when trying to incorporate new methods into the DOM or other pre-existing objects. For instance, I'm attempting to implement a method that can be utilized to display colored text in console logs. Nonetheless, my attempts are resulting in a couple of TypeScript-related issues.

Object.defineProperties(console, {
    redLog: function(msg: string) { console.log(`%c${msg}`, 'color:red'); //TS error: Type '(msg: string) => void' has no properties in common with type 'PropertyDescriptor'.
    },
});

console.redLog("This should print red") //TS error: Property 'redLog' does not exist on type 'Console'.

Do you have any insights into what mistake I might be making? I am uncertain about how to utilize interfaces or any other TypeScript approach that would enable me to add the console.redLog() method. Appreciate any guidance on this! Thanks!

Answer №1

When you want to make changes to already defined objects in TypeScript, there are two essential things you need:

  • A clear definition
  • An implementation that you have completed

If you want TypeScript to recognize a method called redLog on the console, you must identify the type/interface where the definition of console is stored and then enhance it.

In this scenario, the Console interface defines the characteristics of console in the global scope. To add a property to this interface, you must locate the scope where it exists and redefine it accordingly. Your new definition will merge with the existing one seamlessly.

To achieve this, include the following code snippet in your project to re-define the Console interface globally:

declare global {
  interface Console {
    redLog(msg: string): string;
  }
}

By incorporating this definition into your project, your global Console object will be enhanced!

Complete solution

declare global {
  interface Console {
    redLog(msg: string): void;
  }
}

Object.defineProperties(console, {
  redLog: {
    value: function (msg: string) {
      console.log(`%c${msg}`, 'color:red')
    },
  }
});

Playground link

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