Data structures

Question 1

What two main things replace internal tables in JS?

Answer 1

Arrays and Objects

Question 2

How are items in an array separated?

Answer 2

By a comma

Question 3

Give an example of defining an array

Answer 3

Let myArray = [“Bob”,”Tanya”,”Henry”]

Question 4

What is the index of the first item in an array?

Answer 4

0

Question 5

List 5 common array methods

Answer 5

.sort
.reverse
.some
.length
.push
.splice

Question 6

Give the syntax for sorting an array of numbers by ascending and descending order

Answer 6

//sort a number array
Let myArray = [“C”,”D”,”A”,”B”]
myArray.sort(a, b) => a - b); //ascending
myArray.sort((a, b) => b - a);//descending

Question 7

Give the syntax for sorting a non-numeric array

Answer 7

//sort
Let myArray = [“Ann”,”Karen”,”Bobby”];
myArray.sort();
myArray.reverse();

Question 8

What are the two optional parameters for sorting that must be used when sorting numbers?

Answer 8

a = current value
b = next value
so
myArray.sort((a, b) => a - b);
means compare the current value to the next value and if a - b if b is less than a then b needs to move in front of a.
myArray.sort((a, b) => b - a): would be a descending sort. If b is less than a then a should move in front of b as this is descending

Question 9

Explain what the array.some function does and give an example of it’s syntax

Answer 9

The .some searches for a value in the array
Let myArray = [“Bob”,”Henry”,”Karen”]
//check for value Karen
Let found = myArray.some((element) => element === “Karen”);
//Found will have a value of true

Question 10

Give an example of the .length function

Answer 10

let myArray = [“bob”,”henry”,”tanya”];
let myLen = myArray.length();
//mylen will equal 3

Question 11

give an example of the .push function

Answer 11

Let myArray = [“Pasha”,”Misha”];
myArray.push(“Isa”);
//isa will be added to end of the array

Question 12

How is an array written to the console?

Answer 12

Let myArray = [“Isa”,”Bob”];
console.table(myArray);

Question 13

What does the splice function do and what is the syntax?

Answer 13

myArray.splice(
“what index should the insert be
“0 to many lines should be removed
“what should be added
)
//so add “pasha” as the second item
Let myArray = [“Isa”,”Misha”];
myArray.splice(1, 0, “Pasha”];

Question 14

How can an item be deleted from an array?

Answer 14

let myArray = [“Pasha”,”Isa”,”Misha”];
myArray.splice(1,1);
//the above would remove “Isa”

Question 15

How can an item be replaced in an array?

Answer 15

let myArray = [“cat1”,”cat2”,”dog1”]
myArray.splice(0,2,”Dog0”);
//cat1 and cat 2 will be replaced by Dog0
//or
myArray = [“cat”,”dog”,”lizard”];
myArray.splice(1,1,”Isa”,”Pepe”)
//now cat, isa, pepe, lizard

Question 16

What does an object in javascript relate to in ABAP?

Answer 16

A structure

Question 17

what does an object in JS consist of?

Answer 17

name:value pairs

Question 18

give an example of an object in JS

Answer 18

let dog = { breed: “Coton”, name:”Isa” };

Question 19

Can you give an example of an array that uses an object?

Answer 19

let dogArray = [
{
breed: “Coton”,
name: “isa”,
age: 11
},
{
breed: “collie”,
name: “Lassie”,
age: 14
},
];

Question 20

How can an object field be addressed?

Answer 20

let myObj =
{
make: “Buick”,
model: “Wildcat”,
}
console.log(myObj.make);