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JavaScript IIFE — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript IIFE lesson. Every one is checked automatically in the browser — write the code, run it, and the tests tell you what still fails.

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Exercises(5)

  1. 1

    Write an IIFE

    easy10 min

    Use an IIFE to work out 6 times 7 and store the answer.

  2. 2

    Pass an argument

    easy10 min

    Pass the name Ada into an IIFE and return a greeting.

  3. 3

    Keep a variable private

    easy10 min

    Show that a variable inside an IIFE cannot be seen outside.

  4. 4

    Return an object

    easy10 min

    Return a config object from an IIFE and show its version.

  5. 5

    An arrow IIFE

    medium10 min

    Write the same idea as an arrow IIFE returning the word ready.

Find the bug(5)

  1. 1

    Fix the IIFE that never runs

    easy8 min

    Without the final brackets the function is stored, not called.

  2. 2

    Fix the argument in the wrong brackets

    easy8 min

    The argument belongs in the calling brackets.

  3. 3

    Fix the leaked variable

    easy8 min

    The variable is declared outside, so it is not private.

  4. 4

    Fix the missing return

    easy8 min

    The IIFE builds the object but never gives it back.

  5. 5

    Fix the arrow IIFE syntax

    easy8 min

    The arrow function is never invoked.

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