Passing an array to a function
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Which call gives the function total ONE array of scores?
2. You have let myScores = [4, 7, 9]; Which call passes this array to total?
3. In function total(scores) { ... }, what is scores?
4. Which loop header reads every item of the array scores inside the function?
5. What does this print? function first(list) { return list[0]; } console.log(first([5, 6, 7]));
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1function total(scores) { let sum = 0; for (const s of scores) sum += s; return sum; } | AEmpty square brackets after the parameter name are invalid syntax. The array should be used by name or an index. | |
| 2function addBonus(scores) { scores.push(10); } | BThe function receives an array in its parameter and loops over it to add up every item. | |
| 3Call a function and give it an array as the argument | CThe function changes the original array that was passed in by adding an item to it. | |
| 4A function returns a new array and leaves the original array unchanged | Dtotal([4, 7, 9]); | |
| 5function total(scores) { let sum = 0; for (const s of scores) sum += s; } | EThere is no return statement, so the function gives back undefined instead of the total. | |
| 6function largest(scores) { return Math.max(scores[]); } | Ffunction doubleAll(nums) { return nums.map(n => n * 2); } |
C
Definitions
function total(scores)
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
function count(list) {
return list.______;
}
2.
function double(nums) {
return nums.___(n => n * 2);
}
3.
function addItem(list, item) {
list.____(item);
}
4.
const scores = [4, 7, 9];
addItem(______, 5);
console.log(scores);
5.
function show(names) {
for (const n __ names) console.log(n);
}
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
function total(nums) {
B
let sum = 0;
C
nums.forEach(n => sum += n);
D
return sums;
E
}
Question 2
A
function average(nums {
B
let sum = 0;
C
nums.forEach(n => sum += n);
D
return sum / nums.length;
E
}
Question 3
A
function doubleAll(nums) {
B
nums.map(n => n * 2);
C
}
D
const a = [1, 2, 3];
E
console.log(doubleAll(a));
Question 4
A
function bonusAll(marks) {
B
let n = marks.length;
C
for (let i = 0; i < n; i++) {
D
let x = marks[i] + 5;
E
}
F
}
Question 5
A
const marks = [70, 85, 60];
B
function largest(nums) {
C
return Math.max(nums);
D
}
E
console.log(largest(marks));
Answer Key
Passing an array to a function
Section A: Quick Questions
Q1
A — total([4, 7, 9])
Q2
B — total(myScores)
Q3
B — A parameter that holds the array passed in when the function is called
Q4
A — for (let i = 0; i < scores.length; i++)
Q5
A — 5
Section B: Match the Pairs
Q1
function total(scores) { let sum = 0; for (const s of scores) sum += s; return sum; } → The function receives an array in its parameter and loops over it to add up every item.
Q2
function addBonus(scores) { scores.push(10); } → The function changes the original array that was passed in by adding an item to it.
Q3
Call a function and give it an array as the argument → total([4, 7, 9]);
Q4
A function returns a new array and leaves the original array unchanged → function doubleAll(nums) { return nums.map(n => n * 2); }
Q5
function total(scores) { let sum = 0; for (const s of scores) sum += s; } → There is no return statement, so the function gives back undefined instead of the total.
Q6
function largest(scores) { return Math.max(scores[]); } → Empty square brackets after the parameter name are invalid syntax. The array should be used by name or an index.
Section C: Definitions
Q1
function total(scores) — A function with a parameter that receives an array when called, e.g. total([4, 7, 9]). The function can loop over it, return a new array, or change the original array.Section D: Fill in the Blanks
Q1
function count(list) {
return list.length;
}Q2
function double(nums) {
return nums.map(n => n * 2);
}Q3
function addItem(list, item) {
list.push(item);
}Q4
const scores = [4, 7, 9];
addItem(scores, 5);
console.log(scores);Q5
function show(names) {
for (const n of names) console.log(n);
}Section E: Spot the Error
Q1
D — The variable is called sum, not sums, so this causes a ReferenceError. The function should return sum, the total built up while looping over the array.
Q2
A — The closing bracket after the parameter name is missing. It should be function average(nums) {.
Q3
B — map() builds a new array, but without return the function throws it away and gives back undefined. It should be return nums.map(n => n * 2);.
Q4
D — This stores the new mark in a local variable, so the original array is never changed. To change the array passed in, it should be marks[i] += 5;.
Q5
C — Math.max needs separate numbers, so passing the whole array gives NaN. The array must be spread with ...nums: Math.max(...nums).