Declare inside a block — practice exercise

What you'll be asked to do

1. 1.Declare inside a blockexercise · easy · 10 min

   Show that a let variable inside braces does not escape them.

   Passes when: #out should show undefined.

2. 2.A loop variable disappearsexercise · easy · 10 min · practice plan

   Show that a let loop counter does not exist after the loop.

   Passes when: #out should show undefined.

3. 3.var escapes the blockexercise · easy · 10 min · practice plan

   Show that a var declared in a loop is still readable afterwards inside the function.

   Passes when: #out should show 3.

4. 4.Each turn gets its own letexercise · easy · 10 min · practice plan

   Collect three functions from a let loop and show the values they return.

   Passes when: #out should show 1,2,3.

5. 5.const still allows property changesexercise · medium · 10 min · practice plan

   Change a property on a const object and show the new value.

   Passes when: #out should show light.

6. 6.Fix the leaked variablebug fix · easy · 8 min

   Declared outside the block, the variable is not private at all.

   Passes when: #out should show undefined.

7. 7.Fix the var loop bugbug fix · easy · 8 min · practice plan

   All three functions share one var, so they all report the same number.

   Passes when: #out should show 1,2,3.

8. 8.Fix the counter read too latebug fix · easy · 8 min · practice plan

   A let counter does not exist after its loop.

   Passes when: #out should show 3.

9. 9.Fix the branch variable read outsidebug fix · easy · 8 min · practice plan

   The variable is declared inside the if block.

   Passes when: #out should show Pass.

10. 10.Fix the const reassignmentbug fix · easy · 8 min · practice plan

    A const cannot be pointed at a new object, only changed inside.

    Passes when: #out should show light.

Between them these tasks cover let and const, var vs let and Loop bindings.

Looking for a different chapter? See every practice set, or switch to the interview theory questions.