Sample interfaces

export interface Credentials {  
  email: string;
  password: string;
}

export interface User {
  firstName: string;
  lastName: string;
  age: number;
}

Pick constructs a type by picking the set of properties Keys (string literal or union of string literals) from Type

Pick syntax

Pick<Type, Keys>

Example

var newInterface: Pick<Credentials, 'email'> = {} as Pick<Credentials, 'email'>;
//newInterface contains email only

Omit constructs a type by picking all properties from Type and then removing Keys (string literal or union of string literals).

Omit syntax

Omit<Type, Keys>

Example

var newInterface: Pick<Credentials, 'email'> = {} as Pick<Credentials, 'email'>;
//newInterface omits email

Extends multiple interfaces

interface UserCredentials extends Credentials, User { }  //Extends Credentials, User
interface UserCredentials extends Credentials, Pick<User, 'firstName' | 'lastName' > { }  //Extends Credentials, User (firstName, lastName only)
interface UserCredentials extends Credentials, Omit<User, 'firstName' | 'lastName' > { }   //Extends Credentials, User (age only)

The sample JSON file content (data.json):

[
  {
    "FirstName": "Joe",
    "UserId": 1
  },
  {
    "FirstName": "Jack",
    "UserId": 2
  }
]

Next, add appropriate resolveJsonModule entry to tsconfig.json entry

{
    "compilerOptions": {  
      "esModuleInterop": true
      "resolveJsonModule": true
    } 
}

Finally, import the data and access it using the below code.

import data from './data.json';

interface Person{
    FirstName: string,
    UserId: number,
}

const userArray:User[] = data as User[];

Sample environment variables for development & production environment.ts

export const environment = {
    env: 'Dev'
};

environment.prod.ts

export const environment = {
    env: 'Prod'
};

In the above code using the window object like below:
environment.ts

export const environment = {
    env: window['env'] || 'Dev'
};

environment.prod.ts

export const environment = {
    env: window['env'] || 'Prod'
};

Create a .js file in the root directory and add it to index.html file as a script

<script src="./config.js"></script>

In the config.js file, you can update the environment values without rebuilding your application like below:

window['env'] = 'Uat';

You can exclude the Typescript build .js .js.map from VS Code using the below steps.
Add the below code to .vscode folder settings.json file, this will exclude .js and.js when the typescript file present for the corresponding .js and .js.map file

{
    "files.exclude": {
        "**/*.js": {
            "when": "$(basename).ts"
        },
        "**/*.js.map": {
            "when": "$(basename)"
        }
    }
}