Chapter 5

1. Review

• Basic JavaScript
• Prompt Function - Always returns a string
  
• Assignment statements - Connects a variable name with a data value
  
• name = "Mike";
• An actual piece of data is called a literal
  
• Write statements - HTML code that will be formatted on the page
  
• Example of a JavaScript program with prompt, assignment, and write

2. Primitive data types in JavaScript

• Numbers
• No distinction is made between integers and floating-point numbers
• Examples of numeric literals
  
• 3
• 3.15
• 6.02e23 // this means 6.02 times 10 to the 23rd power


• Strings
• A JavaScript string is any sequence of characters
• String literals always appear between single or double quotes
• Examples of string literals
• "Please enter your name"
• "3.15"
• "Mike Hvidsten"
• "This is an example of a \" double-quote \" in a string"



• Booleans
• The boolean type has two values, represented by the keywords true and false

3. Using Numbers

• Use the predefined function parseFloat("3.15") to convert a string ("3.15") into its corresponding number (3.15)


• But we must be careful about concatenation
• "3.15" + "1" evaluates to "3.151" (string concatenation)
• 3.15 + 1 evaluates to 4.15 (numerical addition)
• "3.15" + 1 evaluates to "3.151" (string concatentation)
• Example to add two numbers (needs repair)
• Group Work - fix this program
  

4. Predefined functions

• JavaScript provides an extensive library of predefined functions
• Examples
• document.write("x");
• prompt("","");
• parseFloat(x);
• Math.sqrt(x);
• Math.max(y, y);
  
• Math.random();

5. Expressions and operators

• Expressions are formed by combining values, which may be literals, variables, function calls, array elements, or object properties, using JavaScript operators
• Parentheses are used to group subexpressions and alter the default order of evaluation of operators
• 1 + 2 * 3 is evaluated as 1 + (2 * 3)
• If you really want the addition done before the multiplication, you should write (1 + 2) * 3

6. Group Project

• Write a JavaScript program to prompt for two numbers x and y and that writes out on the web page the square root of x*y.
  
• Add to your program a second output to the web page of the maximum value of x and y.