The answer
With an IIFE (immediately invoked function expression) that captured the current value of i as a parameter. Each iteration created a new function scope, so each callback closed over its own copy.
let and const in Loops: The Closure Fix
How did developers fix the var loop closure bug before let existed?
More FAQs in let and const in Loops: The Closure Fix
Because let creates a fresh binding of the loop variable per iteration. Each callback closes over its own copy of i, which holds the value for that iteration. With var, all callbacks share one i, which is the final value by the time they run.
No. const i = 0; i++; throws TypeError because i++ reassigns i, and const does not allow reassignment. Use let for classic for loop counters.
Yes. Each iteration of for...of creates a fresh binding, and the loop variable does not change within an iteration. const is appropriate and preferred for for...of and for...in.
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