Variables and data types

Question 1

JS in loosely typed. What does that mean?

Answer 1

It means that a variable can be defined with just a name. Things like lenght and type are not declared

Question 2

Are variables case sensitive

Answer 2

Yes

Question 3

What must variables begin with

Answer 3

a character

Question 4

What value will an variable with an unassigned value return?

Answer 4

Undefined

Question 5

How many primitive data types are in JS?

Answer 5

Undefined
Number
String
Boolean
Object
Structural type

Question 6

Give an example of an undefined data type

Answer 6

Var car;

Question 7

Give an example of a number data type

Answer 7

var myweight = 20;

Question 8

Give an example of a string data type

Answer 8

var dogname = “Isa”;

Question 9

Give an example of a boolean data type

Answer 9

var theswitch = false;

Question 10

Give an example of a number array data type

Answer 10

varnumarray = [1,3,5,7,9];

Question 11

Give an example of an object data type

Answer 11

var myobj = {firstname:”Bob”,lastname:”Heide”};

Question 12

Why are JS types considered dynamic?

Answer 12

Because the type changes based on the value of the var. For example var myname = “bob”; is a strin but I can then say myname = 3; and that changes the type to numeric

Question 13

How can i display the type of a variable?

Answer 13

console.log(typeof myname);

Question 14

What is the data type of the following statement
var fruit = “apple” + 3;

Answer 14

The type is string because it is set by the first part of the value which is a string

Question 15

What would the value of the variable be? What would it’s type be?

var mynum = 5 + 3 + “gift”;

Answer 15

The answer is 8gift.
JavaScript moves left to right. In this case the numbers are treated as math and then the string is added. This makes the type string

Question 16

What is Global scope in JS?

Answer 16

A variable defined outside of an actual function. For example
var car = “BMW”;
Function showCar( ) {
console.log(car);
}
showCar( );
Car is a global variable available in the function

Question 17

What is local scope in JS?

Answer 17

function showCar() {
var car = “BWM”;
console.log(car);
}
showCar(); /*will list the car /
console.log(car); /this will fail because car was created as a local var not a global. Outside of the function it does not exist

Question 18

What is meant by local scope:block scope?

Answer 18

Think of this like the “let” statement in ABAP. The block scope is local to the keyword if you will. For example
function test() {
if (true)
var1 = “BMW”;
let car2 = “AUDI”;
}
In the above scenario car2 is only valid within the if statement in which it is declared

Question 19

In modern syntax what two new ways of declaring variables exist?

Answer 19

let and const
These allow us to create block scope variables

Question 20

What is the difference between let and const

Answer 20

think of const as a constant in ABAP. It is declared with a value and the value cannot be changed.
const firstName = “John” will always be John. You can’t then say
firstName = “Bob”

Question 21

What string method returns the length of the string?

Answer 21

let alpha = “abcdef”;
console.log(‘String length is ${alphabet.length}’);

Question 22

What string method finds a value in a string?

Answer 22

let alpha = “Where ever you go there you are”;
console.log(‘Go lies at index: ${alpha.indexOf(“go”)}’);

Question 23

What method allows the reduction of decimal places?

Answer 23

let num1 = 5.1234;
console.log(num1.toFixed(2)); // 5.12

Question 24

How can a string be converted to a number and vice versa

Answer 24

let num1 = 14.33
console.log(typeof num1);
let numString = num1.toString();
let num2 = Number(num1)
-this example is from page 23 of the book and makes little sense