Object Prototype custom function [ Angular 7.2 - TS 3.2 ]

Question

im try to create a global prototype with a custom function.

I need this:

console.log({'active':1, 'profile':1}._state())

{'active':true,'profile':1,'state':'root'}

I try this:

global.ts

declare global {
    interface Object {
        _state(): Object;
    }
}

Object.prototype._state = function (): Object {
    if (this.active === 1) {
        this.active = true;
    }

    if (this.profile === 1) {
        this.state = 'root';
    }

    return this;
};

export {};

When I try to use, fail with this error:

TS2339: Property '_state()' does not exist on type {'active':1, 'profile':1}

And in my class say component.ts

import '. /global.ts';

@Injectable()
export class AppState{

    constructor(){
       console.log({'active':1, 'profile':1}._state());
    }
}

TS2345: Argument of type 'AppState' is not assignable to parameter of type 'Object'

Federico Galfione · Accepted Answer · 2019-05-14 12:47:08Z

1

So try to change the code in your file like this:

global.ts

interface Object{
  _state(): Object; 
}

Object.prototype._state = function() {
  if (this.active === 1) {
        this.active = true;
    }
    if (this.profile === 1) {
        this.state = 'root';
    }
    return this;
}

Then you have to insert the interface inside your typings.d.ts, so the compiler knows there is a change in Object.

typings.d.ts

interface Object{
  _state(): Object; 
}

In the end import your global file inside your module.

app.module.ts

// make sure the path is right
import './global.ts';

That should do the trick. I've tried it and the console.log works like a charm.

answered May 14, 2019 at 12:47

Federico Galfione

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