JavaScript Introduction Terms

Question 1

What is JavaScript?

Answer 1

It is a programming language that powers the dynamic behavior on most websites. Alongside HTML and CSS, it is a core technology that makes the web run.

Question 2

What are Methods?

Answer 2

Methods return information about an object and are called by appending an instance with a period “.”, the method name, and parentheses. Example: Math.random(); // Returns a number between 0 and 1

Question 3

What is a console.log()?

Answer 3

The console.log() method is used to log or print messages to the console. It can also be used to print objects and other info.

Question 4

What is String Concatenation?

Answer 4

In JavaScript, multiple strings can be concatenated together using the “+” operator.

Question 5

What is an Assignment Operator?

Answer 5

An assignment operator assigns a value to its left operand based on the value of its right operand.

Question 6

What is the addition assignment operator?

Answer 6

+=

Question 7

What is the subtraction assignment operator?

Answer 7

-=

Question 8

What is the multiplication assignment operator?

Answer 8

*=

Question 9

What is the division assignment operator?

Answer 9

/=

Question 10

What is String Interpolation?

Answer 10

It is the process of evaluating string literals containing one or more placeholders (expressions, variables, etc). It can be performed using template literals: “text ${expression} text”. “‘Tommy is ${age} years old.’;”

Question 11

What are Variables?

Answer 11

A variable is a container for data that is stored in computer memory. It is referenced by a descriptive name that a programmer can call to assign a specific value and retrieve it.

Question 12

What does Undefined mean?

Answer 12

“undefined” is a primitive JavaScript value that represents lack of defined value. Variables that are declared but not initialized to a value will have the value “undefined”.

Question 13

How do you declare a variable?

Answer 13

To declare a variable in JavaScript, any of these keywords can be used along with a variable name: var, let, and const.

Question 14

When is the variable “var” used?

Answer 14

“var” is used in pre-ES6 versions of JavaScript.

Question 15

When is the variable “let” used?

Answer 15

“let” is the preferred way to declare a variable when it can be reassigned. A “let” variable will contain “undefined” if nothing is assigned to it.

Question 16

When is the variable “const” used?

Answer 16

“const” is the preferred way to declare a variable with a constant value. It must have an assignment. Any attempt of reassigning a “const” variable will result in a JavaScript runtime error.

Question 17

What are Template Literals?

Answer 17

Template literals are strings that allow embedded expressions, for example: ${expression}. While regular strings use single ‘ or double “ quotes, template literals use backticks `` instead. Example: console.log(Hello, ${name});

Question 18

What are Built-in Objects?

Answer 18

Built-in objects contain methods that can be called by appending the object name with a period “.”, the method name, and a set of parentheses. Example: Math.random(); // “Math” is the built-in object

Question 19

What does String.length mean?

Answer 19

The “.length” property of a string returns the number of characters that make up the string. Example: console.log(‘howdy’.length); // Prints: 5

Question 20

What are Booleans?

Answer 20

Booleans are a primitive data type. They can either be “true” or “false”. Example: let lateToWork = true;

Question 21

What are Single Line Comments?

Answer 21

In JavaScript, single-line comments are created with two consecutive forward slashes //. Example: // This line will denote a comment

Question 22

What does Null mean?

Answer 22

Null is a primitive data type. It represents the intentional absence of a value. In code, it is represented as “null”.

Question 23

What are Strings?

Answer 23

Strings are a primitive data type. They are any grouping of characters (letters, spaces, numbers, or symbols) surrounded by single quotes ‘ or double “ quotes. Example: let single = ‘Where is my hat?’; or let double = “Where is my hat?”;

Question 24

What is the Remainder / Modulo Operator?

Answer 24

The remainder operator, sometimes called modulo, returns the number that remains after the right-hand number divides into the left-hand number as many times as it evenly can. Example: const daysLeftOver = 365 % 7 ;