Expanding the functionality of the Typescript number data type

I am trying to enhance the functionality of the number type. Here is the code I attempted:

interface NumberExtension
{
    IsInRange(min: number, max: number):boolean;
}

Number.prototype.IsInRange = function(min: number, max: number): boolean
{
    if ((this >= min) && (this <= max)) return true;

    return false;
}

I saved this in a file named extensions.ts inside the src/app/common directory. Is this the correct location?

However, my code is not compiling and I am getting an error message:

Property 'IsInRange' does not exist on type 'number'.

Interestingly, my editor (Visual Studio Code) is not showing any errors. What could be causing this issue? I suspect that TypeScript's number is different from the NumberExtension interface.

Answer №1

Include a handy utility function in your toolkit:

export function checkRange(value: number, min: number, max: number): boolean {
  return value >= min && value <= max
}

You can apply it to your code like this:

const isWithinRange = checkRange(7, 3, 12); // instead of 7.checkRange(3, 12)

Answer №2

It is recommended to place the number interface at the top of your .ts file

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