undefined
any variable that has not been
assigned a value and
any property of an object
that does not exist
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null
indicates that variable has been
declared but defined empty
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number
• values that can be
processed and calculated
• can be positive or negative
• represented internally as a
double, accurate to 14 or 15
digits
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number
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number calculations
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Math!
http://www.w3schools.com/jsref/jsref_obj_math.asp
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string
• sequence of characters
enclosed with quotation marks
• can use single or double quotes
• cannot use quotes of the same
type inside the same type
unless they are escaped
http://www.w3schools.com/jS/js_obj_string.asp
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string characters
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string characters
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everything is
zero indexed
j a v a s c r i p t
0 1 2 3 4 5 6 7 8 9
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string characters
(shortcut)
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string characters
(shortcut)
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string escaping
cannot use quotes of the same type inside
the same type unless they are escaped
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same quotes
no escape
FAIL!
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meet the escape
character
\
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same quotes
with escape
WIN!
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same quotes
no escape
FAIL!
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same quotes
with escape
WIN!
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different quotes
WIN!
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different quotes
WIN!
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string length
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string search
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changing string case
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string to number
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string to number
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string to number
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“class is awesome”.charAt(2)
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“class is awesome”.charAt(2)
“a”
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“class is awesome”[0]
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“class is awesome”[0]
“c”
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how do I get the length of
“football”
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how do I get the length of
“football”
“football”.length
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“football”.length
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“football”.length
8
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“football”.indexOf(‘e’)
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“football”.indexOf(‘e’)
-1
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“football”.indexOf(‘foot’)
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“football”.indexOf(‘foot’)
0
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what type is: ‘asdf’
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what type is: ‘asdf’
“string”
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what type is: 15
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what type is: 15
“number”
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what type is: -’15’
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what type is: -’15’
“number”
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10 + 20
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10 + 20
30
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boolean
true or false
http://www.w3schools.com/jS/js_obj_boolean.asp
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