Chap. 4 eloquent javascript

Question 1

let listOfNumbers = [2, 3, 5, 7, 11];
console.log(listOfNumbers[2]);

console. log(listOfNumbers[0]);
console. log(listOfNumbers[2 - 1]);

Answer 1

// → 5
// → 2
// → 3

Question 2

Almost all JavaScript values have properties. The exceptions are______ and________.

Answer 2

null

undefined

Question 3

true or false?

null has properties

Answer 3

false

Question 4

The two main ways to access properties in JavaScript are with a _________ and with ____________.

Answer 4

dot notation

square brackets

Question 5

null.length;

returns?

Answer 5

// → TypeError: null has no properties

Question 6

Write in bracket notation

array.length

Answer 6

array[‘length’]

Question 7

Write in dot notation

array[‘length’]

Answer 7

array.length

Question 8

let doh = "Doh";
console.log(typeof doh.toUpperCase);

Answer 8

// → function

Question 9

let doh = "Doh";
console.log(doh.toUpperCase());

Answer 9

// → DOH

Question 10

let sequence = [1, 2, 3];

sequence. push(4);
sequence. push(5);
console. log(sequence);

Answer 10

// → [1, 2, 3, 4, 5]

Question 11

let sequence = [1, 2, 3, 4, 5];
console.log(sequence.pop());

console.log(sequence);

Answer 11

// →5

// → [1, 2, 3, 4]

Question 12

let day1 = {
  squirrel: false,
  events: ["work", "touched tree", "pizza", "running"]
};

console. log(day1.squirrel);
console. log(day1.wolf);

day1. wolf = false;
console. log(day1.wolf);

Answer 12

// → false
// → undefined
// → false

Question 13

Properties in objects whose names aren’t valid binding names or valid numbers have to be_________.

Answer 13

quoted

Question 14

let anObject = {left: 1, right: 2};
console.log(anObject.left);
// → 
delete anObject.left;

console.log(“left” in anObject);
// →
console.log(“right” in anObject);
// →

Answer 14

// → 1

// → false
// → true

Question 15

To find out what properties an object has, you can use the ___________ function

Answer 15

Object.keys

Question 16

console.log(Object.keys({x: 0, y: 0, z: 2}));
// →

Answer 16

// → [“x”, “y”, “z”]

Question 17

There’s an ___________ function that copies all properties from one object into another.

Answer 17

Object.assign

Question 18

let object1 = {value: 10};
let object2 = object1;
let object3 = {value: 10};

console.log(object1 == object2);
// →
console.log(object1 == object3);
// →

Answer 18

// → true

// → false

Question 19

let object1 = {value: 10};
let object2 = object1;
let object3 = {value: 10};
object1.value = 15;

console.log(object2.value);
// →
console.log(object3.value);
// →

Answer 19

// → 15
// → 10

Question 20

The _________ method returns the first index at which a given element can be found in the array, or -1 if it is not present.

Answer 20

indexOf()

Question 21

The indexOf() method returns the first index at which a given element can be found in the array, or _____ if it is not present.

Answer 21

-1

Question 22

The ____________ method returns the last index at which a given element can be found in the array, or -1 if it is not present.

Answer 22

lastIndexOf()

Question 23

The________ method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included). The original array will not be modified.

Answer 23

Slice()

Question 24

let kim = "Kim";
kim.age = 88;
console.log(kim.age);
// →

Answer 24

// → undefined

Question 25

The __________ method returns the first index at which a given element can be found in the array, or -1 if it is not present.

Answer 25

indexOf()

Question 26

console.log("one two three".indexOf("ee"));
// →

Answer 26

// → 11

Question 27

The ________ method removes whitespace (spaces, newlines, tabs, and similar characters) from the start and end of a string.

Answer 27

trim

Question 28

let anObject = {left: 1, right: 2};

console.log(anObject.left);
// →

Answer 28

// → 1

Question 29

The _________method splits a String object into an array of strings by separating the string into substrings, using a specified separator string to determine where to make each split.

Answer 29

split()

Question 30

let sentence = "Secretarybirds specialize in stomping";
let words = sentence.split(" ");
console.log(words);

returns?

Answer 30

// → [“Secretarybirds”, “specialize”, “in”, “stomping”]

Question 31

The _______ method creates and returns a new string by concatenating all of the elements in an array (or an array-like object), separated by commas or a specified separator string.

Answer 31

join()

Question 32

You can use a similar _________ notation to call a function with an array of arguments

Answer 32

three-dot