JavaScript Arrays

Question 1

What is an Array?

Definition

Answer 1

The JavaScript Array object is a global object that is used in the construction of arrays; which are high-level, list-like objects.

Question 2

Array Syntax

Answer 2

var fruits = [‘Apple’, ‘Banana’]; console.log(fruits.length); // 2

var first = fruits[0]; // Apple var last = fruits[fruits.length - 1]; // Banana

Question 3

What does index mean?

Answer 3

The count starts at 0

Question 4

Are arrays indexed?

Answer 4

Yes

Question 5

An example of an idexed array…

Answer 5

var example = [1 , 12, “Aaron”, 4, “Scott”, true]

example [2]

returns Aaron

Question 6

What is push?

Answer 6

Add something to the end of an array.

colors.push (“blue”);

Question 7

What is a pop?

Answer 7

Add something to the begining of an array.

colors.pop (“blue”);

Question 8

Whst is a shift in an array?

Answer 8

Remove something from the begining of an array.

colors.shift (“blue”);

Question 9

What is a Unshift in an array?

Answer 9

Add something to the begining of an array.

colors.uhshift (“blue”);

Question 10

What is indexOf in an array?

Answer 10

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

Question 11

What is the syntax of indexOf in an array?

Answer 11

var a = [2, 9, 9];

a. indexOf(2); // 0
a. indexOf(7); // -1

Question 12

What is slice in an array?

Answer 12

The slice() 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.

Question 13

What is the syntax of slice in an array?

Answer 13

var a = [‘zero’, ‘one’, ‘two’, ‘three’];

var sliced = a.slice(1, 3);

console.log(a); // [‘zero’, ‘one’, ‘two’, ‘three’] console.log(sliced); // [‘one’, ‘two’]

Question 14

What is a nested array?

Answer 14

Arrays can be nested, meaning that an array can contain another array as an element. Using this characteristic of JavaScript arrays, multi-dimensional arrays can be created.

Question 15

What is the syntax of a nested array?

Answer 15

var a = new Array(4);

for (i = 0; i < 4; i++) {

a[i] = new Array(4);

for (j = 0; j < 4; j++) {

a[i][j] = ‘[’ + i + ‘, ‘ + j + ‘]’;

}

}