Conditionally initializing a constant in Javascript

Question

ES6 onwards we have const.

This is not allowed:

const x; //declare first
//and then initialize it
if(condition) x = 5;
else x = 10;
         


        

Answer 1

If ternary operator isn't an option for its unreadability, the only other option is IIFE, which is cumbersome but can be read fluently:

const x = (() => {
  if (condition)
    return 5
  else
    return 10
})();

The semantics of const is that it is assigned once. It should be let for this use case:

let x;
if(condition) x = 5;
else x = 10;

From my personal experience, ~95% of variables are const. If a variable has to be be let, just let it be itself; the probability of bugs caused by accidental reassignments is negligible.