how to add a const in javascript code example

Example 1: 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.

Example 2: constants in js

static methodName() { ... }
static propertyName [= value];