return versus console.log inside a function

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Quick Questions

Shade in the A or B circle for each question.

1. A function has the line return total; What does that line do?

A Hands total back to the code that called the function

B Only prints total in the console and gives nothing back

2. function add(a, b) { console.log(a + b); } let answer = add(2, 3); What is stored in answer?

A 5

B undefined

3. Which function lets you save its result in a variable?

A function double(n) { return n * 2; }

B function double(n) { console.log(n * 2); }

4. What does console.log(total) do inside a function?

A Sends the value back to the line that called the function

B Shows the value in the console but does not give it back

5. You want to use a function's answer in a later calculation, like let cost = price(3) + 5;. What should price() do?

A Use return to give back the price

B Use console.log to show the price

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1function add(a, b) { return a + b; }		AThe function logs the value instead of returning it, so result is undefined. Use return n * 2; instead.
2function add(a, b) { console.log(a + b); }		Bfunction showScore(score) { console.log(score); }
3To save a function's answer in a variable, the function must return the value.		Clet total = add(2, 3); // add uses return
4If you only want to display a message for the user to read, console.log is enough.		DHands the sum back to the caller, so it can be stored in a variable or used in other code.
5function double(n) { console.log(n * 2); } let result = double(4); console.log(result); // undefined		EOnly shows the sum in the console. The function gives back undefined, so there is nothing to store.
6function square(n) { return n * n; } square(5);		FThe returned value is never used. Store it with let answer = square(5); or show it with console.log(square(5)).

Definitions

return

Fill in the Blanks

Complete each line of code by filling in the missing parts.

function double(n) { ______ n * 2; }

function square(n) { return n * n; } let result = ______(4); console.log(result);

function show(n) { console.log(n * 2); } let x = show(5); console.log(x); // _________

function add(a, b) { return a + b; } let sum = add(2, 3); ___________(sum);

function getAge() { ______ 13; } let age = getAge() + 1; console.log(age);

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A function add(a, b) (

B return a + b;

C }

D let total = add(2, 3);

E console.log(total);

Question 2

A function square(n) {

B console.log(n * n);

C }

D let result = square(4);

E console.log(result);

Question 3

A function getGreeting(name) {

B 'Hi ' + name;

C }

D let msg = getGreeting('Sam');

E console.log(msg);

Question 4

A function area(w, h) {

B let a = w * h;

C console.log(a);

D }

E let size = area(3, 4);

Question 5

A function isEven() {

B return n % 2 === 0;

C }

D console.log(isEven(6));

Answer Key

return versus console.log inside a function

Section A: Quick Questions

A — Hands total back to the code that called the function

B — undefined

A — function double(n) { return n * 2; }

B — Shows the value in the console but does not give it back

A — Use return to give back the price

Section B: Match the Pairs

function add(a, b) { return a + b; } → Hands the sum back to the caller, so it can be stored in a variable or used in other code.

function add(a, b) { console.log(a + b); } → Only shows the sum in the console. The function gives back undefined, so there is nothing to store.

To save a function's answer in a variable, the function must return the value. → let total = add(2, 3); // add uses return

If you only want to display a message for the user to read, console.log is enough. → function showScore(score) { console.log(score); }

function double(n) { console.log(n * 2); } let result = double(4); console.log(result); // undefined → The function logs the value instead of returning it, so result is undefined. Use return n * 2; instead.

function square(n) { return n * n; } square(5); → The returned value is never used. Store it with let answer = square(5); or show it with console.log(square(5)).

Section C: Definitions

return — Hands a value back to the code that called the function so it can be stored or used. console.log only shows a value in the console, so a function that only logs gives back undefined.

Section D: Fill in the Blanks

function double(n) {
  return n * 2;
}

function square(n) { return n * n; }
let result = square(4);
console.log(result);

function show(n) { console.log(n * 2); }
let x = show(5);
console.log(x); // undefined

function add(a, b) { return a + b; }
let sum = add(2, 3);
console.log(sum);

function getAge() { return 13; }
let age = getAge() + 1;
console.log(age);

Section E: Spot the Error

A — A function body must open with a curly brace {, not a bracket (. The line should be function add(a, b) {. Then return a + b can hand the sum back to the caller.

B — console.log only shows the value in the console. It does not give it back, so result would be undefined. The line should be return n * n; so the value goes back to the caller.

B — The text is joined but never returned, so the function gives back undefined and msg holds undefined. The line should be return 'Hi ' + name;

C — Logging a only displays it. The function then gives back undefined, so size would be undefined. The line should be return a; so the area is handed back to the caller.

A — The function uses n but has no parameter to receive the value, so n is not defined inside it. The line should be function isEven(n) {