Midterm Study

Introduction to Web Pages

1. A web page is a container for the following three technologies. Describe the purpose of each for a web page:
• HTML
• CSS
• JavaScript

Answers:

• HTML is used for defining web elements and the rough layout of a website
• CSS is used to style the default HTML elements
• JavaScript is used for data input, manipulation and other logical components

Introduction to javascript

1. Browser pop-up dialogue box functions
• alert()
• prompt()
• confirm()

Answers:

• Reload webpage to see examples

Data Types and Variables

1. Name JavaScript's three data types. Describe the types of data they store
2. JavaScript is a weakly-typed language. Describe what this means.
3. What are the naming rules for a variables name? What are naming conventions?
4. What is a constant in JavaScript? Describe how you would declare a JavaScript constant.

Answers:

1. Number, String and Boolean
2. weakly-typed language implies that data types do not need to be defined at initialization, the compiler will decide, cast and convert the data type unless explicitly cast
3. A naming convention is a recommended way of naming variables to ensure readability and organize code. JavaScript uses camelCase for variables and classes and UPPER_SNAKE_CASE for constants
let customerAge = 23;
const ONT_TAX_RATE = 0.13;
4. A constant is a variable whose value cannot be changed once initialized, making it constant. To define a constant, use the "const" keyword.

Operators

1. Explain the following binary operators: + - * / %
2. Explain the multiple uses of the + operator.
3. Describe how the increment/decrement operators (++ and --) work.

Answers:

1. The + operator is used to get the sum, the - operator is to get the difference, the * operator multiplies, the / operator divides and the % (modulus) operator determines if two numbers divided have a remainder and how much of one
2. The + operator can be used to add two numbers together to find their sum, or you can use it to concatenate multiple Strings together.
3. The ++ (increment) operator is used to increase the value of a variable by exactly one. The -- (decrement) operator is used to decrease the value of a variable by exactly 1.

The JavaScript Math object

1. Describe the operation and the return for the following Math methods:
• Math.PI
• Math.abs(x)
• Math.pow(x,2)
• Math.round(x)
• Math.ceil(x)
• Math.floor(x)
• Math.trunc(x)
• Math.random()
• Math.min(x,y)
• Math.max(x,y)

Answers:

• Math.PI is a constant value for PI
• Math.abs(x) returns the absolute value of X (makes a negative positive)
• Math.pow(x,2) returns the value of x to the power of y (in this case 2)
• Math.round(x) returns x rounded to the nearest whole. Below 0.5 is rounded down, above 0.5 is rouded up.
• Math.ceil(x) returns the "ceiling" of x, which is the next highest whole integer.
• Math.floor(x) returns the "floor" of x, which is the next lowest whole integer.
• Math.trunc(x) returns x truncated, which means it cuts off the decimal places regardless of what they are.
• Math.random() returns a random number between 0 and 1, can be manipulated to return in between any range
• Math.min(x,y) returns the minimum of two numbers. The smaller of the two
• Math.max(x,y) returns the maximum of two numbers. The larger of the two

JavaScript Number Methods

1. Describe the operation and the return for the following Number methods:
• toFixed()
• toPrecision()

Answers:

• toFixed() returns x but at a fixed number of decimal places, defined by y
• toPrecision() returns x but at a fixed number of significant digits. This means it may round deicimal places before dropping them.

JavaScript Global Functions

1. Describe the operation and the return for the following global functions:
• parseInt(number)
• parseFloat(number)

Answers:

• parseInt(number) takes a string as input and returns the first integer in the string. Can also accept a radix option
• parseFloat(number) takes a string as input and returns the first float value in the string.

JavaScript String Methods

1. Describe the operation and the return for the following String methods.
• length
• toLowerCase()
• toUpperCase()
• charAt()

Answers:

• length gets the character count of a string including spaces
• toLowerCase() turns all uppercase letters to lowercase letters
• toUpperCase() turns all lowercase letters to uppercase letters
• chatAt() takes a number for the index of the word to search through and returns the character at that index.

Playground

Interactive JavaScript follows