JS Course 1: Fundamental 5 String/Array Methods

Question 1

What does filter() do?

Answer 1

This method is used to filter through an array only including certain items.

Question 2

What does map() do?

Answer 2

This method is used to do something to every single item in an array. Some things you could do to every item is reformat them, add or takeaway something from them, etc.

Question 3

What does sort() do?

Answer 3

This method is used to sort an array by a certain designated order. It can also slyly be used to do something to every item in an array.

Question 4

What does reduce() do?

Answer 4

This method is used to work with every single item in an array, working with a total amount and each item in the array individually.

Question 5

What does reduceRight() do?

Answer 5

This method does the same as reduce(), but works from the right of the array to the left.

Question 6

What does Array.from() do?

Answer 6

This method returns an array from any iterable object, like a string for instance.

Question 7

What does includes() do?

Answer 7

This method works on array and returns a boolean value on if the array contains a certain value in it.

Question 8

What does some() do?

Answer 8

This method checks if at least on thing in your array meets what you’re looking for and returns a boolean value.

Question 9

What does every() do?

Answer 9

This method checks if all things in your array meet what you’re looking for, very similar to some()’s syntax.

Question 10

What does find() do?

Answer 10

This method is similar to filter() but instead of returning a subset of the array you’re working with, it returns JUST the one you are looking for. Specifically, it finds and returns the very first item that meets the criteria you specify.

Question 11

What does findIndex() do?

Answer 11

This method is the exact same as find(), but returns the index position of the item that first meets the criteria, which is your parameter.

Question 12

What does findLastIndex() do?

Answer 12

Same as findIndex() but works from the back of the array. Aka, right to left.

Question 13

What does the […SPREAD] operator do?

Answer 13

This operator takes an iterable, like a string or object and allows us to quickly copy all or part of an existing array or objects into another array or object.

You can think of it as being the opposite of a rest parameter, though they look exactly the same!

Question 14

What does push() do?

Answer 14

This method adds items to the end of the array. The parameter is what you wish to add to the end of the array.

Question 15

What does pop() do?

Answer 15

This method extracts the item at the end of the array.

Question 16

What does shift() do?

Answer 16

This method extracts the item at the beginning of the array.

Question 17

What does unshift() do?

Answer 17

This method adds items to the beginning of the array. The parameter is what you wish to add to the beginning of the array.

Question 18

What does splice() do?

Answer 18

This method primarily is used to delete items from an array, but can be used in a variety of other ways.

Question 19

What does slice() do?

Answer 19

This method is similar to splice() but simpler. It takes two parameters: 1st is where you want to start your slice, and 2nd is where you want to end your slice NOT including the position where the 2nd is.

Question 20

What does concat() do?

Answer 20

This method takes an array (before the .) and arguments (inside ()) and concatenates them together left to right. This method can take on (about) infinite arguments to concatenate together.

Question 21

What does Symbol.isConcatSpreadable do?

Answer 21

Symbol.isConcatSpreadable can be applied as a property with the value true in an object to make it so if the object is concatenated into a new array, it will allow the values in it to be concatenated, and so the object will not be added as a whole.

Question 22

What does forEach() do?

Answer 22

This method allows you to run a function for every element in array. In other words, allows you to iterate through the array doing something to each of it.

Question 23

What does indexOf() do?

Answer 23

This method is used to find the index of an item name and returns the index number. If the item cannot be found, it returns -1.

Question 24

What does lastIndexOf() do?

Answer 24

Same as indexOf(), but starting from the back of the array. Aka, right to left.

Question 25

What does localeCompare() do?

Answer 25

This string method is used on strings so you are able to correctly compare strings.

Question 26

What does reverse() do?

Answer 26

This method reverses the order of elements in an array.

Question 27

What does split() do?

Answer 27

This method allows you to take a string and split it into several parts based on the parameter in the parentheses. The outcome of this method is a new array with values from the string.

Question 28

What does join() do?

Answer 28

This method is very similar to split(), but the other way around. It takes an array and joins all the items together back into a string.

Question 29

What does Array.isArray() do?

Answer 29

This method is used to test if an array is an array or not. It returns a boolean value.

Question 30

What is “thisArg” do?

Answer 30

This keyword is applicable to many array methods like find(), filter(), and map() where you can insert an optional parameter named thisArg.

It’s rarely used so this section is just good to know.

Question 31

What does flat() do?

Answer 31

This method is used to flatten out an array, aka make it so all items are the same depth.

Question 32

What does parseInt() do?

Answer 32

This method takes a string (or really even a number) and turns it into a number input. It works similar to the unary plus operator.