JS week 1 day 3

Question 1

Why do we log things to the console?

Answer 1

The JavaScript console is a debugging tool. It is where the browser prints errors and warnings as they occur in your JavaScript code.

Question 2

How is a method different from any other function?

Answer 2

A function lives on its own. A method is a function associated with an object property. A function can be called directly by its name. A method consists of a code that can be called by the name of its object and its method name using dot notation or square bracket notation.

Question 3

How do you remove the last element from an array?

Answer 3

using .pop method

Question 4

How do you round a number down to the nearest integer?

Answer 4

using Math.floor method

Question 5

How do you round a number down to the nearest integer?

Answer 5

using Math.floor() method

Question 6

How do you generate a random number?

Answer 6

using Math.random() method

Question 7

How do you delete an element from an array?

Answer 7

using .splice method()

Question 8

How do you append an element to an array?

Answer 8

using .push() method

Question 9

How do you break a string up into an array?

Answer 9

using .split() method

Question 10

Do string methods change the original string? How would you check if you weren’t sure?

Answer 10

The split() method does not change the original string because JavaScript strings are immutable. To check we can either check documentation or use console.log()

Question 11

Roughly how many array methods are there according to the MDN Web docs?

Answer 11

38 methods

Question 12

Is the return value of a function or method useful in every situation?

Answer 12

Some functions don’t return any value (For example: void or undefined). Generally, a return value is used where the function is an intermediate step in a calculation of some kind.

Question 13

Roughly how many array methods are there according to the MDN Web docs?

Answer 13

36 methods

Question 14

Give 6 examples of comparison operators.

Answer 14

===, >, =, <=, !===

Question 15

What is the purpose of an if statement?

Answer 15

if statements are used to check if condition is true or false.

Question 16

What data type do comparison expressions evaluate to?

Answer 16

boolean

Question 17

Describe the syntax (structure) of an if statement.

Answer 17

if ( condition) {
return
}

Question 18

What are the three logical operators?

Answer 18

&& and, || or, ! not

Question 19

Describe the syntax (structure) of an if statement.

Answer 19

if keyword, condition inside parenthesis, opening curly brace, code to execute if value is true or false, closing curly brace

Question 20

What does the ++ increment operator do?

Answer 20

increments by 1

Question 21

What is the purpose of a loop?

Answer 21

Loops check a condition; if it returns true, code block will run and will repeat until condition returns false.

Question 22

What is the purpose of a condition expression in a loop?

Answer 22

The condition is an expression that is evaluated once before every iteration. The statement inside the loop is executed only when the condition evaluates to true. The loop is terminated if the condition evaluates to false.

Question 23

What does “iteration” mean in the context of loops?

Answer 23

Iteration is when the same procedure is repeated multiple times.

Question 24

When does the condition expression of a while loop get evaluated?

Answer 24

as long as the condition in the parentheses is true.

Question 25

When does the initialization expression of a for loop get evaluated?

Answer 25

The initialization expression initializes the loop. The initialization expression is executed only once when the loop starts.

Question 26

When does the condition expression of a for loop get evaluated?

Answer 26

as long as the counter is less than the total number specified.

Question 27

When does the condition expression of a for loop get evaluated?

Answer 27

after the initialization expression.

Question 28

Besides a return statement, which exits its entire function block, which keyword exits a loop before its condition expression evaluates to false?

Answer 28

break keyword

Question 29

What does the ++ increment operator do?

Answer 29

increments (adds one to) its operand and returns a value

Question 30

How do you iterate through the keys of an object?

Answer 30

for in loop

Question 31

What is Array.prototype.filter useful for?

Answer 31

The filter() method creates a new array with all elements that pass the test implemented by the provided function. If we need to work with filtered values from a given array.

Question 32

What is Array.prototype.map useful for?

Answer 32

The map() method creates a new array populated with the results of calling a provided function on every element in the calling array.