How do I read a local JSON file in Angular 12?

Question

I am trying to read data from a local JSON file, that stores some config data for my app. I keep getting an error when using the ng build command in the Angular CLI.

The TypeScript file for my component: my-component.ts

...
import credentials from './config/credentials.json';

export class MyComponent implements OnInit {
    ...
    // Properties
    username: string = credentials.username;
    ...
}

The JSON config file, stored at the location '/config': credentials.json

{
    "credentials" : {
        "username" : "my_user_name",
        ...
    }
}

I am getting the error: Error: Should not import the named export 'credentials' (imported as 'credentials') from default-exporting module (only default export is available soon)

What is causing this error? It seems similar to the issue described here.

score 3 · Accepted Answer · answered Jun 03 '21 at 19:27

There are two additional things you need to do for Angular version 12.

First, you need to add some lines to the file. Reference this question here. NOTE: these are different than Angular version 11.

{
    ...
        "compilerOptions": {
            ...
            "resolveJsonModule": true, // add this line...
            "esModuleInterop": true, // this line...
            ...
        },
    ...
    "allowSyntheticDefaultImports": true // and this line, notice this one is outside of "compiler options"
}

Second, you need to add a let statement. The above didn't work for me alone, but by also taking this step, I got it to work. Reference this blog post.

The TypeScript file for my component: my-component.ts

...
import credentials from './config/credentials.json';

let my_username = credentials.username;  // ADD THIS LINE

export class MyComponent implements OnInit {
    ...
    // Properties
    username: string = my_username; // NOW USE THE NEW VARIABLE
    ...
}

Admittedly I do not fully understand why this works, but it works. This source seems to suggest it has to do with variable scoping.

How do I read a local JSON file in Angular 12?

1 Answers1

Linked