Eloquent JavaScript Exercises

Question 1

Write program to output:
#
##
###
####
#####
######
#######

Answer 1

for (let hash = '#'; hash.length <= 7; hash += '#') {
	console.log(hash);
}

Question 2

How do you define and invoke a function? Use simple syntax.

Answer 2

function name(parameter1, parameter2, parameter3) {
    code to be executed
}
ex:
function square(x, x)

Question 3

What are parameters within a function?

Answer 3

Parameters act as placeholders for values within a function. These values will be filled when the function is invoked.

Question 4

What is a and b in the below? What do the ( ) that surround a and b represent? 
function myFunction(a , b){
console.log(a + b);
}

Answer 4

a and b are the parameters of the function.

the parenthesis surrounding a and b are “arguments”. This function has arguments.

Question 5

Call the processArg function with an argument of 7 and assign its return value to the variable processed.

var processed = 0;

function processArg(num) {
  return (num + 3) / 5;
}

Answer 5

processed = processArg(7);

Question 6

What does this program do?
// Setup
var lastName = "Lovelace";

// Only change code below this line.
var lastLetterOfLastName = lastName[lastName.length - 1];

Answer 6

It sets the lastLetterOfLastName variable to the last letter in the lastName variable’s string. In this case it would be the letter “e”.

Question 7

What is a nested array called?

Answer 7

Multi-dimensional Array

Question 8

How is data accessed inside of an array? What encapsulates this data?

Answer 8

Accessed by indexes. Brackets [ ] are what encapsulate the indexes of an array.

Question 9

var arr = [
    [1,2,3],
    [4,5,6],
    [7,8,9],
    [[10,11,12], 13, 14]
];

//equals????
arr[3];
arr[3][0];
arr[3][0][1];

Answer 9

arr[3]; // equals [[10,11,12], 13, 14]
arr[3][0]; // equals [10,11,12]
arr[3][0][1]; // equals 11

Question 10

What does the function .push() do?

What is arr now?
var arr = [1,2,3];
arr.push(4);

Answer 10

.push() takes one or more parameters and “pushes” them onto the end of the array.

// arr is now [1,2,3,4]

Remember that .push() ADDS another index to the end of the array.

Question 11

What does .pop() do and what is the variable myArray = and removedFromMyArray = now?

// Setup
var myArray = [["John", 23], ["cat", 2]];

// Only change code below this line.
var removedFromMyArray = myArray.pop();

Answer 11

.pop() literally pops off the last index in an array and assigns it to a new variable.

So, myArray now equals [“John”, 23]; and removedFromMyArray equals [“cat”, 2];

Question 12

What does the function .shift() do?

What does ourArray equal now?
var ourArray = ["Stimpson", "J", ["cat"]];
removedFromOurArray = ourArray.shift();

Answer 12

.shift() is similar to .pop() except that is removes the first index item in the array and assigns it to a new variable.

So, ourArray now equals [“J”,[“cat”]]; and removedFromOurArray equals [“Stimpson”];

Question 13

What does the function .unshift() do?

What do the variables below equal now?

var ourArray = [“Stimpson”, “J”, “cat”];
ourArray.shift();
ourArray.unshift(“Happy”);

Answer 13

.unshift() works exactly like .push(), but instead of adding the element at the end of the array, unshift() adds the element at the beginning of the array.

var ourArray = [“Stimpson”, “J”, “cat”];
ourArray.shift(); // ourArray now equals [“J”, “cat”]
ourArray.unshift(“Happy”);
// ourArray now equals [“Happy”, “J”, “cat”]