Scope repair

Goal: fix a script whose functions crash with ReferenceError because they look for variables in rooms where those variables can't be seen.

What you're given

The starter file has two functions and one line above them:

• lastMultiple(step, limit) should give back the largest multiple of step that is at most limit, or 0 if there is none.
• sumOfSquares(n) should give back 1*1 + 2*2 + ... + n*n, or 0 when n is 0.
• const demo = lastMultiple(7, 50); sits at the top of the file, above both functions.

The starter doesn't work yet. Run node scope_repair.js in your terminal and you'll see a ReferenceError.

Worked example

And once the file runs, demo must equal 49.

Rules

• Keep function lastMultiple(step, limit) and function sumOfSquares(n) as function declarations with these names.
• Keep the line const demo = lastMultiple(7, 50); above the two functions. Don't move it down.
• Both functions must return their answers, and must give the same answer every time they're called with the same inputs.
• Neither function may leave anything behind in the global scope: every box they use must be made with let or const in a room where it can be seen.
• Don't use var.
• To look at things yourself, add a line such as console.log(demo, sumOfSquares(3)); at the bottom, then remove it.

What you'll practice

• Reading a ReferenceError and working out which room it points at
• Block scope: where a box made inside curly braces can and can't be seen
• Why a declared function can be used from a line above it
• Loops that build up a result

Run it

gonomicon fetch fs-week-2/02-04-scope-repair
cd 02-04-scope-repair
gonomicon test
gonomicon submit

Hints

1. Run node scope_repair.js and read the ReferenceError out loud: it names a variable, and says it can't be seen. Ask two questions: in which room was that box made, and from which room is the code asking for it?
2. A box made with let or const inside the curly braces of a loop lives only inside those braces. If you need its value after the loop, make the box before the loop and only change it inside. And a name that was never made anywhere (like total) has to be made with let before you use it.
3. In lastMultiple: put let best = 0; above the for, and inside the loop write best = n * step; with no let. In sumOfSquares: put let total = 0; above the loop. Leave the const demo line where it is, above the functions.