Arrays, date, random
Declared Variables
• Explicitly define them
• Can give them starting values
• Figures out type
• Case sensitive
var x = 5; (note: this is the ONLY use of =)
Arrays
• Collection of related information
• Referenced with index
• Easy way to choose between items
var array = [ “A", "B", “F", "G" ];
• Just keep adding items!
array[index]
• Start with 0
• Example: user enters number, you return that month
Random Selection
• Choose between options randomly
var n = Math.random();
• [Math is a collection of functions]
• Need to save it to reuse!
• Returns value between 0 and 1
Converting Random to Integer
• Often useful to convert that random number to an integer
• Index into array!
• 0->1 needs to be changed to 0->3 (or any other number)
var biggerNumber = n*4; gets the range correct
• But only want integer:
• Math.floor returns the largest integer less than the value
var biggerInteger = Math.floor(n*4);
Conditional Examples
• Random message using if
• Simple if…then…else
• Condition is random function
Date and Time
Full date is unfriendly format
• To get today’s date: var d = new Date();
• To get the time: var time = d.getHours();
• To get the day: var theDay = d.getDay();
w3schools
http://www.w3schools.com/js/js_date_methods.asp
What does it mean?
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Objects have attributes
Chair: color, size, legs, wheels, …
Date: year, month, day, day of week, hour, …
Object.retrieve-attribute
Assign the date with built-in function Date()
Extract the piece using getHours, getDays, …
Date and Time Examples
• 3 messages based on Hour
• Prints an appropriate message based on time
of day (3 choices)
• 2 messages based on Day
• Prints an appropriate message based on day of
week (2 choices)