Answers for "typescript declare variable undefined"

typescript declare variable undefined

let age: number | undefined;
age = 18;

if (age) {
  // This will run because age is not null or undefined
}

age = undefined;

if (age) {
  // This will not run because age is undefined
}

// If you want to do something when it is undefined
if (age === undefined) {
  // This will run because age is undefined
}

string undefined typescript

let name1:string = person.name!; 
//                            ^ note the exclamation mark here