A code sample from the article: https://www.joshwulf.com/blog/2020/02/providing-a-semantic-api/

signature.ts

//global variable
const GlobalMembersArray  =[];

// TypeScript types on function parameters
function Member({id, password}: {id: string, password: string}){
  this.id          = id; 
  this.password    = password
}
  
const member1 = new Member({id: "m001", password: "123"});

GlobalMembersArray.push(member1);