constants in javasript, code example

Example 1: how to dec are a constant in javascript

const myBirthday = '18.04.1982';

Example 2: what is const in javascript

const age; // errror as const cannot be kept un-initialized;
const age = 20 ; 
const age = 21 , // error as once declared const variable cann't be
// re-declared in same scope or different scope.