JavaScript

1
JavaScript

• Variable Names Literals

2
JavaScript Datatypes

• Numbers (integer and real)
• Ex. 42, 3.14159
• Boolean values
• Ex. True or False
• Strings
• Ex. MFHS, Computer Science
• Null
• Ex. null

3
DataType Conversion

• You do NOT have to specify the datatype of a
  variable when you declare it. Datatypes are
  automatically converted as needed during the
  course of script execution.
• Defining a variable
• var answer 50
• Reassigning the same variable
• answer Yes

Holding a number
Holding a string
4
Variable Names

• The "Golden Rules" of Variables
• Variable names may contain any combination of
  letters, numbers, and the underscore ('_')
  character, but may only begin with a letter or
  underscore.
• A variable's name should describe what it does.
• All variables must be declared using the var
  command.
• Examples
• First_Name
• num5
• _super

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Scope of a Variable

• Global
• You can use the variable anywhere in the
  application
• Ex. var total 0
• Local
• You can use the variable within the current
  function
• Ex. var total 0

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Literals

• String Literals
• Enclosed in either single or double quotes
• blah
• blah
• 1234
• Null
• Used to represent variables which have not been
  initialized

• Integers
• Can be expressed in decimal(base10),
  hexadecimal(base16), or octal(base8) format.
• Floating Point Literals
• Decimal point 3.1415
• Exponent 2.5E3
• Signs -3.5e-2
• Boolean
• true or false

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Special Characters

• \b backspace
• \f form feed
• \n new line character
• \r carriage return
• \t tab character
• Quote inside of quote
• I like the movie \Top Gun \with Tom Cruise
• I like the movie Top Gun with Tom Cruise