how to create a constant file in the ionic 3?

Question

What is the best/recommended way to set a global constant to be used across the entire app, like an API URL string?

I have the JSON format and want to set a global constant and use across the entire app as a static. import { Injectable } from '@angular/core';

@Injectable() export class Service { item_data = [ { item_id:'1', item_image: "assets/img/bluesaphire.jpg", item_title:'Blue Saphire Stone' } ];

Answer 1

Very Simple! Just follow these two steps -

1) Create an Injectable class (eg. AppConstants) in a root directory (eg. src) with required properties

2) Import it in your component class constructor & use wherever needed

So, your app.constants.ts would be like -

import { Injectable } from '@angular/core';

@Injectable({
    providedIn: 'root'
})
public class AppConstants {
    public item_data = [
        { item_id:'1', item_image: "assets/img/bluesaphire.jpg",  item_title:'Blue Saphire Stone' } 
    ];
}

And, use it as -

// here, config is a directory & app.constants is a ts file
import { AppConstants } from '../../config/app.constants';    // update your way

public class TestComponent {
    // dependency injection
    constructor(private constants: AppConstants) { }

    testMethod() {
        // using it here
        console.log(this.constants.item_data);
    }
}

Answer 2

Environment Variables can is a good way to handle this. See example:

https://medium.com/prototype-berlin/a-simple-way-to-use-environment-variables-in-ionic-3-12641dc55b55