Enhancing native JavaScript types in TypeScript 1.8 with the power of global augmentation

Currently, I am working on expanding the capabilities of native JavaScript types using the new global augmentation feature in TypeScript 1.8, as detailed in this resource. However, I'm encountering difficulties when the extension functions return the same type.

Global.ts

export {};
declare global {
    interface Date {
        Copy(): Date;
    }
}

if (!Date.prototype.Copy) {
    Date.prototype.Copy = function () {
        return new Date(this.valueOf());
    };
}

DateHelper.ts

export class DateHelper {
    public static CopyDate(date: Date): Date {
        return date.Copy();
    }
}

Upon trying to utilize the defined extension in DateHelper.ts, I encountered error TS2322:

Type 'Date' is not assignable to type 'Date'.
Property 'toDateString' is missing in type 'Date'.

I am seeking assistance in resolving this issue. Does anyone have a solution?

Answer №1

Here is a method you can use to copy a Date object:

Create a file called Global.ts:

interface Date 
{
    Copy: () => Date;
}

Date.prototype.Copy = function() 
{
    return new Date(this.valueOf());
};

In another file, DateHelper.ts:

import './Global';

export class DateHelper {
    public static CopyDate(date: Date): Date {
        return date.Copy();
    }
}

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