Check out example codes for "typeof typescript". It will help you in understanding the concepts better.

Code Example 1

// simple type
type Websites = 'www.google.com' | 'reddit.com';
let mySite: Websites = 'www.google.com' //pass
//or
let mySite: Website = 'www.yahoo.com' //error
// the above line will show error because Website type will only accept 2 strings either 'www.google.com' or 'reddit.com'.
// another example. 
type Details = { id: number, name: string, age: number };
let student: Details = { id: 803, name: 'Max', age: 13 }; // pass
//or 
let student: Details = { id: 803, name: 'Max', age: 13, address: 'Delhi' } // error
// the above line will show error because 'address' property is not assignable for Details type variables.
//or
let student: Details = { id: 803, name: 'Max', age: '13' }; // error
// the above line will show error because string value can't be assign to the age value, only numbers.

Code Example 2

typeof undefined; // "undefined"
typeof true;      // "boolean"
typeof 1337;      // "number"
typeof "foo";     // "string"
typeof {};        // "object"
typeof parseInt;  // "function"
typeof Symbol();  // "symbol"

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