Array prototype TypeScript

Question

I have created my own extensions to Array as below:

export interface Func<T, TResult> {
    (item: T): TResult;
}

declare global {
    interface Array<T> {
        where(predicate: Func<T, boolean>): Array<T>;
        single(predicate: Func<T, boolean>): T;
        first(predicate: Func<T, boolean>): T;
        take(predicate: Func<T, boolean>, count: number): Array<T>;
        countWhere(predicate: Func<T, boolean>): number;
        count(): number;
    }
}

Array.prototype.count = function <T>(): number {
    return this.length;
}

//others

In any of my component intellisense shows me these methods as extensions but while debugging I get undefined for example:

events: Event[];
var result = this.events.count();

Where should I implement Array methods so they could be visible from any component?

Have you loaded the module that actually creates these methods in your debugged project? — Bergi, Feb 16 '17 at 17:04
Its in diffrent .ts file I have exportem this file in used component — miechooy, Feb 16 '17 at 17:14
did you ever do an import of this file? Anywhere? it should be just import 'path-to-my-file'; — toskv, Feb 16 '17 at 17:37
I have imported this file in component where methods are used — miechooy, Feb 16 '17 at 17:47

score 0 · Answer 1 · answered Feb 17 '17 at 06:48

Here are the things to check...

Whether the file containing extensions loads
Whether it loads in the correct order (i.e. before it is used)

Open up the developer tools in your web browser (usually F12) and select the "Network" tab.

Run your application and review the JavaScript files that load.

You can check that the file containing your Array extensions is loaded - and that it is loaded before the file that depends on these extensions.

Array prototype TypeScript

1 Answers1