Methods

Question 1

.concat()

Answer 1

Joins two or more arrays. Format array1.concat(array2, array3).

Question 2

constructor

Answer 2

returns information on the constructor used to make the array/object/function/whatever.

Question 3

.copyWithin()

Answer 3

Copies the first two array elements to the last two array elements. Deletes the original last two elements. Doesn’t work with IE 11

Question 4

.entries()

Answer 4

Breaks an array into a series of key/value pairs. Among other things, used when converting data to objects.

Question 5

every()

Answer 5

checks if every value in an array passes a test. Used for quality control, defensive programming, and more.

Question 6

fill()

Answer 6

Fills an array with a static variable (Static variables can only be changed by the function they appear in, so they hold their value between functions AND don’t take a global scope).

You can specify where variables start getting filled in with the following syntax- fill(variable, start, end).

If no start or end is specified, the whole array is filled in.

Warning: This will over write the original array.

Question 7

.filter()

Answer 7

Returns a new array with the filtered elements. Takes a function

Question 8

.find()

Answer 8

Finds and returns the first element of an array that passes a test (provided as a function). Does this by iterating over every element in the array. Stops when it finds the first value that passes. If no itempass the test, returns undefined.

Question 9

.findIndex()

Answer 9

Finds and returns the index of the first element that passes a test, (provided as a function). Stops when it finds the first value that passes. If no items pass the test, returns -1.

Question 10

.forEach()

Answer 10

Calls a function on each element of an array. Does not return a new array.

Question 11

.map()

Answer 11

Calls a function on each element of an array, then returns a new array.

Question 12

.from()

Answer 12

creates an array from a string.

Question 13

.includes()

Answer 13

Checks an Array for a specific value. If the value is found, returns true, otherwise returns false. Note: Its case sensitive.

Question 14

.indexOf()

Answer 14

returns the index of the array element. If no element is found, returns -1.

Question 15

.isArray()

Answer 15

Returns true if the object is an array.

Question 16

.join()

Answer 16

returns an array as a string. Does not change the original array.

Question 17

.keys()

Answer 17

Returns the keys (indexes) of an array, as an iteration object.

Question 18

.valueOf()

Answer 18

Returns the value of the array. The ‘default’ method of the array.

Question 19

.length

Answer 19

Returns the length of the array.

Question 20

.lastIndexof()

Answer 20

The same as .indexOf() but starts from the end of the array, to hopefully find the last occurrence of an item in an array.

Question 21

.pop()

Answer 21

removes the last element of an array and returns that element.

Question 22

prototype

Answer 22

The prototype constructor allows you to add new properties and methods to the Array() object.

When constructing a property, ALL arrays will be given the property, and its value, as default.

When constructing a method, ALL arrays will have this method available.

Note: Array.prototype does not refer to a single array, but to the Array() object itself.

Note: Prototype is a global object constructor which is available for all JavaScript objects.