Read after declaring — practice exercise

What you'll be asked to do

1. 1.Read after declaringexercise · easy · 10 min

   Declare a let and read it on the next line.

   Passes when: #out should show ready.

2. 2.Catch a TDZ errorexercise · easy · 10 min · practice plan

   Use try and catch to show the word caught when a let is read too early.

   Passes when: #out should show caught.

3. 3.typeof is safe for undeclared namesexercise · easy · 10 min · practice plan

   Show what typeof gives for a name that was never declared.

   Passes when: #out should show undefined.

4. 4.var has no dead zoneexercise · easy · 10 min · practice plan

   Show that a var read before its line is undefined rather than an error.

   Passes when: #out should show undefined.

5. 5.Declare at the top of the blockexercise · medium · 10 min · practice plan

   Declare everything before use and return a greeting for Ada.

   Passes when: #out should show Hello Ada.

6. 6.Fix the read before the declarationbug fix · easy · 8 min

   A let cannot be read above its own line.

   Passes when: #out should show ready.

7. 7.Fix the missing catchbug fix · easy · 8 min · practice plan

   Without a catch the error is never turned into a message.

   Passes when: #out should show caught.

8. 8.Fix the const used too earlybug fix · easy · 8 min · practice plan

   A const has the same dead zone as a let.

   Passes when: #out should show 120.

9. 9.Fix the inner declaration read too soonbug fix · easy · 8 min · practice plan

   Inside the block, the inner name is in charge from the opening brace.

   Passes when: #out should show inner.

10. 10.Fix the greeting built too earlybug fix · easy · 8 min · practice plan

    The greeting word is used before it is declared.

    Passes when: #out should show Hello Ada.

Between them these tasks cover Temporal dead zone, let and const errors and Declaration order.

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