What is the typeof operator? How is it used in TypeScript?

TypeScript - Interview Questions

Similar to JavaScript, the typeof operator in TypeScript returns the type of the operand as a string.

console.log(typeof 10);  // "number"
console.log(typeof 'foo');  // "string"
console.log(typeof false);  // "boolean"
console.log(typeof bar);  // "undefined"

In TypeScript, you can use the typeof operator in a type context to refer to the type of a property or a variable.

let greeting = "hello";
let typeOfGreeting: typeof greeting;  // similar to let typeOfGreeting: string