const or let in React component

Question

const is a signal that the variable won’t be reassigned.

let is a signal that the variable may be reassigned

Additional things to ponder:

Use const by default
Use let only if rebinding is needed
const does not indicate that a value is ‘constant’ or immutable.
```
const foo = {};
foo.bar = 10;
console.log(foo.bar); // --> 10
```
Only the binding is immutable. ie using an assignment operator or a unary or postfix — or ++ operator on a const variable throws a TypeError exception
ES6 const and let are hoisted too. Although the identifiers has the same memory reference from compile time, they cannot be accessed before declaration in the code. (but not as we thought the declaration would be physically moved to the top in the scope) 😉