# MCS-170 The Nature of Computer Science

## 1. Using Numbers in JavaScript - Part II

• Use the predefined function `parseFloat("3.15")` to convert a string (`"3.15"`) into its corresponding number (`3.15`)
• myNumber = prompt("Enter a number", "");    Returns a String
• myNumber = parseFloat(myNumber);   Converts the string data to a number
• Large numbers are expressed in Scientific Notation
• `6.02e23 // this means 6.02 times 10 to the 23rd power`
• Numbers in JavaScript are represented in memory cells of 64-bits
• This means only a finite range of numbers can be stored!
• Example  (1e308 is a number, 1e309 is too big!)
• Largest number is 1.79E+308
• Smallest (positive) number is 5e-324
• Predefined Numeric Functions:
• Math.sqrt(x);       returns the square root of x
• Math.max(a,b);   returns the larger of a and b
• Math.min(x,y);   returns the smaller of x and y
• Math.pow(x,y);  returns x to the y power
• Math.abs(n);       returns the absolute value of n
• Math.floor(y);     returns the largest integer less than or equal to y
• Math.ceil(x);       returns the smallest integer greater than or equal to x
• Math.round(a);    returns the rounded-off integer to a
• Math.random();   returns a random number that is greater than or equal to 0 and less than 1.
• Example (Discuss how math functions work)

## 2. Using Strings in JavaScript

• A JavaScript string is any sequence of characters
• String literals always appear between quotes
• Examples of string literals
• `"Please enter your name"`
• `"3.15"`
• `'Mickey Mouse'`
• ```"This is an example of a \" double-quote \" used in a string"```
• Example

## 3. Review for Exam 1

• You may bring in a notebook-sized paper with your notes written on one side.
No computer-generated printout allowed.
• Review the Chapter Summaries at the end of Chapters 1, 2, 3, 4, and 5
• Review the Homework sets 1 and 2
• Review the Ideas presented in the Projects
• Exam will have tree types of questions:
• True - False
• Short description of terms
• HTML and JavaScript
• Be prepared to write HTML code for illustrating various document components such as links, bold text, paragraphs, etc.
• Be prepared to write JavaScript commands to carry out the five capabilities discussed so far:
• prompting for input
• using variables
• writing to a web page
• converting strings to numbers
• using pre-defined functions