when to use const and let code example

Example 1: let vs const

`const` is a signal that the identifier won't be reassigned.

`let` is a signal that the variable may be reassigned, such as a counter in a
loop, or a value swap in an algorithm.

It also signals that the variable will be used only in the block it's defined
in, which is not always the entire containing function.

Example 2: why use const and not let?

const only prevents re-assigning, it doesn't make the entire object immutable. ... It's useful to use const instead of let , because it prevents you from accidentally overwriting variables