Arrays

Question 1

Set the ‘mixture’ variable to an array with 3 string elements, 2 numbers and one boolean.

Answer 1

var mixture = [“a”, “b”, “c”, 1, 2, true];

Question 2

Set the variable ‘guides’ that has placeholders for 42 elements but has no values stored in it.

Answer 2

var guides = new Array(42);

Question 3

var myArray = [“sugar”, “rush”, “fix”, “it”, 3.14, 42];

Get the 3rd element in ‘myArray’ to the variable ‘thirdElementInArray’.

Answer 3

var thirdElementInArray = myArray[2];

Question 4

var myArray = [“sugar”, “rush”, “fix”, “it”, 3.14, 42];

Set the 31st element in ‘myArray’ to the word ‘treehouse’.

Answer 4

myArray[30] = “treehouse”;

Question 5

var spareWords = [“The”,”chimney”,”sweep’s”,”dog”];

Use a method on the ‘spareWords’ to set ‘firstWord’ to be the first word of the ‘spareWords’ array whilst simultaneously removing it from the beginning of the array.

Answer 5

var firstWord = spareWords.shift();

• removes and returns the first value in the array

Question 6

var spareWords = [“The”,”chimney”,”sweep’s”,”dog”];

Use a method on the ‘spareWords’ to set ‘lastWord’ to be the last word of the ‘spareWords’ array whilst simultaneously removing it from the end of the array.

Answer 6

var lastWord = spareWords.pop();

• removes and returns the last value in the array

Question 7

var spareWords = ["The","chimney","sweep's","dog"];
var saying = ["quick", "brown", "fox", "jumps", "over", "the", "lazy"];
var firstWord = spareWords.shift();
var lastWord = spareWords.pop();

Add the ‘firstWord’ variable to the beginning of the array ‘saying’.

Answer 7

saying. unshift(firstWord);

- prepends a value to the beginning of the array

Question 8

var spareWords = ["The","chimney","sweep's","dog"];
var saying = ["quick", "brown", "fox", "jumps", "over", "the", "lazy"];
var firstWord = spareWords.shift();
var lastWord = spareWords.pop();

Add the ‘lastWord’ variable to the end of the array ‘saying’.

Answer 8

saying. push(lastWord);

- appends a value to the end of the array

Question 9

var saying1 = [“The”, “quick”, “brown”, “fox”, “jumps”, “over”, “the”, “lazy”, “dog”];

Modify ‘saying1’ so it’s in the opposite order.

Answer 9

saying1.reverse();

Question 10

var saying2 = [“The”, “quick”, “brown”, “fox”, “jumped”, “over”, “the”, “lazy”, “dog’s”, “back”];

Sort the ‘saying2’ array, so that the words are listed in length order. The shortest first. Use the ‘length’ property on the strings in the sort function.

Answer 10

saying2.sort(function(a, b) {
return a.length-b.length;
});

Question 11

var first =  ["The", "quick", "brown", "fox", "jumps"]
var second =  ["over", "the", "lazy"];

Set the variable ‘saying’ to the concatenation of the ‘first’ and ‘second’ arrays with the word “dog”.

Answer 11

var saying = first.concat(second).concat(“dog”);

• appends all of the values to the array in order

Question 12

var first =  ["The", "quick", "brown", "fox", "jumps"]
var second =  ["over", "the", "lazy"];
var saying = first.concat(second).concat("dog");

Set the variable ‘shortSaying’ to be a slice of the ‘saying’ array to include the strings of “quick”, “brown”, and “fox”.

Answer 12

var shortSaying = saying.slice(1, 4);

• returns a new array based on the array from index start to index end

Question 13

var first =  ["The", "quick", "brown", "fox", "jumps"]
var second =  ["over", "the", "lazy"];
var saying = first.concat(second).concat("dog");

Set the ‘sayingString’ variable to the string of all the strings in ‘saying’ joined together by spaces.

Answer 13

var sayingString = saying.join(“ “);

• returns a string with all values in array joined with the string separator

Question 14

var saying = [“The”, “quick”, “brown”, “fox”, “jumps”, “over”, “the”, “lazy”, “dog”];

Use the ‘splice’ method to replace “quick” and “brown” from the ‘saying’ array and add “slow” and “red” in their place in that order.

Answer 14

saying.splice(1, 2, “slow”, “red”);

Question 15

In the following code, what value would be stored in result?

var values = ["Treehouse", "Adventure", "Frog"];
var result = values[3];

Answer 15

undefined

Question 16

What is the final value of the array values after this code is executed?

var values = ["Treehouse", "Island", "Adventure"];
values.splice(1, 1, "Jungle", "Ambassador");

Answer 16

[“Treehouse”, “Jungle”, “Ambassador”, “Adventure”]

Question 17

What piece of code would replace the value “Adventure” with “Island”?

var values = [“Treehouse”, “Adventure”, “Frog”];

Answer 17

values[1] = “Island”;

Question 18

What does the push( ) method do to an array?

Answer 18

it takes a value and appends it to the end of the array

Question 19

Given the following array, what would evaluate to the value “Treehouse”?

var values = [“Treehouse”, “Adventure”, “Frog”];

Answer 19

values[0];

Question 20

What is the the length of this array?

var values = [1, 2, [3, 4, 5], 6];

Answer 20

4

Question 21

What does the pop( ) method do to an array?

Answer 21

removes and returns the last value of that array

Question 22

Given the following code, how are array1 and array2 modified when concat is called?

var array1 = [1, 2, 3];
var array2 = [3, 4, 5];
var array3 = array1.concat(array2);

Answer 22

neither array1 nor array2 are modified after they are created

Question 23

When creating an array with the syntax new Array(argument), what is the argument passed to Array?

Answer 23

the initial length of the array