inventor

Anders Hejlsberg

• Original author of Turbo Pascal
• Chief architect of Delphi
• Lead architect of C#
• Core developer on TypeScript

TypeScript is not executable language
We should translate it first

what we can do in javascript
but can't do in TypeScript

let jsVar = 0; 
jsVar = "js"; 

this code in js will brake the program

let aNumber = 123;
aNumber = {
  name: "John",
  age: 23
}

but can be fixed in ts

let aNumber: number = 123;

js code example:

function isEligible(personObj) {
  return personObj.age > 34;
}

let john = {
  name: "John",
  age: 23
};

isEligible(john);

ts solution:

interface Person {
  name: string;
  age: number;
}
function isEligible(personObj: Person) {
  return personObj.age;
}
let john = {
  name: "John",
  age: 23
};
isEligible(john);

that's all
thank you!