Javascript Syntax: Intro

Question 1

console.log()

Answer 1

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 2

JavaScript

Answer 2

JavaScript 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 3

Methods

Answer 3

Methods return information about an object, and are called by appending an instance with a period ., the method name, and parentheses.

Question 4

Libraries

Answer 4

Libraries contain methods that can be called by appending the library name with a period ., the method name, and a set of parentheses.

Question 5

Numbers

Answer 5

Numbers are a primitive data type. They include the set of all integers and floating point numbers.

Question 6

String .length

Answer 6

The .length property of a string returns the number of characters that make up the string.

Question 7

Data Instances

Answer 7

When a new piece of data is introduced into a JavaScript program, the program keeps track of it in an instance of that data type. An instance is an individual case of a data type.

Question 8

Booleans

Answer 8

Booleans are a primitive data type. They can be either true or false.

Question 9

Math.random()

Answer 9

The Math.random() function returns a floating-point, random number in the range from 0 (inclusive) up to but not including 1.

Question 10

Math.floor()

Answer 10

The Math.floor() function returns the largest integer less than or equal to the given number.

Question 11

Single Line Comments

Answer 11

In JavaScript, single-line comments are created with two consecutive forward slashes //.

Question 12

Null

Answer 12

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

Question 13

Strings

Answer 13

Strings are a primitive data type. They are any grouping of characters (letters, spaces, numbers, or symbols) surrounded by single quotes ‘ or double quotes “.

Question 14

Arithmetic Operators

Answer 14

JavaScript supports arithmetic operators for:

\+ addition
- subtraction
* multiplication
/ division
% modulo

Question 15

Multi-line Comments

Answer 15

In JavaScript, multi-line comments are created by surrounding the lines with /* at the beginning and */ at the end. Comments are good ways for a variety of reasons like explaining a code block or indicating some hints, etc.

Question 16

Remainder / Modulo Operator

Answer 16

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.

Question 17

Assignment Operators

Answer 17

An assignment operator assigns a value to its left operand based on the value of its right operand. Here are some of them:

\+= addition assignment
-= subtraction assignment
*= multiplication assignment
/= division assignment

Question 18

String Interpolation

Answer 18

String interpolation 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.

Question 19

Variables

Answer 19

Variables are used whenever there’s a need to store a piece of data. A variable contains data that can be used in the program elsewhere. Using variables also ensures code re-usability since it can be used to replace the same value in multiple places.

Question 20

Undefined

Answer 20

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 21

Learn Javascript: Variables

Answer 21

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 22

Declaring Variables

Answer 22

To declare a variable in JavaScript, any of these three keywords can be used along with a variable name:

var is used in pre-ES6 versions of JavaScript.
let is the preferred way to declare a variable when it can be reassigned.
const is the preferred way to declare a variable with a constant value.

Question 23

Template Literals

Answer 23

Template literals are strings that allow embedded expressions, ${expression}. While regular strings use single ‘ or double “ quotes, template literals use backticks instead.

Question 24

let Keyword

Answer 24

let creates a local variable in JavaScript & can be re-assigned. Initialization during the declaration of a let variable is optional. A let variable will contain undefined if nothing is assigned to it.

Question 25

const Keyword

Answer 25

A constant variable can be declared using the keyword const. It must have an assignment. Any attempt of re-assigning a const variable will result in JavaScript runtime error.

Question 26

String Concatenation

Answer 26

In JavaScript, multiple strings can be concatenated together using the + operator. In the example, multiple strings and variables containing string values have been concatenated. After execution of the code block, the displayText variable will contain the concatenated string.