String Manipulation

1
Chapter 8

• String Manipulation

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Background

• We already looked at the String object (Chapter
  4)
• length
• charAt()
• indexOf()
• substr() and substring()
• toUpperCase() and toLowerCase()
• Now well look at some very powerful other
  methods
• split()
• match()
• replace()
• search()

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The split() Method

• Splits a string into an array of substrings based
  on the location and existence of separators
• Separation parameter
• var myString A,B,C
• var myTextArray myString.split(,)
• ch8_examp1.htm Example

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The replace() Method

• Used to search for a substring within a string
  and where it finds it, it replaces it with the
  replacement substring specified.
• var myString The event will occur in May, the
  21st of May
• myCleanedupString myString.replace(May,June
  )
• The event will occur in June, the 21st of June

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The search() Method

• Allows you to search a string for a particular
  piece of text.
• If found, the character position is returned. If
  not found, a 1 is returned

6
The match() Method

• Returns an array of all matches resulting from
  searching for a string within some text
• Most useful when used with regular expressions

7
Regular Expressions

• Provide a means of defining a pattern of
  characters, which are used to split, search, or
  replace characters in a string where they fit the
  defined pattern
• RegExp object
• A simple example

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Regular Expressions Special Characters
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Regular Expressions Special Characters
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Regular Expressions Special Characters
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Regular Expressions Special Characters

• ch8_examp2.htm Example
• Checks to see if a string you enter contains only
  letters and numbers
• RegExp is an Object and has Methods
• .test

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Regular Expressions Repetition Characters
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Regular Expressions Repetition Characters
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Regular Expressions Repetition Characters

• Examples
• \d-\d\d\d-\d\d\d\d
• Can be rewritten as
• \d-\d3-\d4
• Paula? Matches Paul or Paula

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Regular Expressions Position Characters
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Regular Expressions Position Characters
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Regular Expressions Position Characters

• Examples
• myPattern
• Matches an occurrence of myPattern if it is at
  the beginning of a line.
• myPattern
• Matches an occurrence of myPattern if it is at
  the end of a line.
• Boundaries
• boundaries.htm

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Integrating

• Complex string replacement
• Paul, Paula, Paulina, paul, Paul
• Want this to convert to
• Ringo, Paula, Paulina, Ringo, Ringo
• var myRegExp /Paul/gi
• Ringo, Ringoa, Ringoina, Ringo, Ringo
• var myRegExp /Paul\W/gi
• \W matches any non-word character so this regular
  expression matches occurrences of Paul followed
  by a non-word character.
• Ringo Paula, Paulina, Ringo Paul
• Note the missing commas and final occurrence of
  Paul

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Integrating

• One more try using boundaries
• var myRegExp /Paul\b/gi
• Ringo, Paula, Paulina, Ringo, Ringo
• Add another wrinkle
• Paul, Paula, Paulina, paul, Paul, JeanPaul
• var myRegExp /\bPaul\b/gi

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Grouping Regular Expressions

• Use () to group characters into patterns that we
  then apply repetition characters to
• grouping regular expressions.htm
• var myString "JavaScript, VBScript and Perl"
• var myRegExp /\b(VB)?(Java)?Script\b/gi

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Grouping Regular Expressions

• Matching repeating characters
• A small hypothetical situation
• 009,007,001,002,004,003 is Valid
• 007,007,001,002,002,003 is not
• \d
• \d,
• \d,700
• (\d),\1
• repeating character.htm

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The split() Method

• Allows us to split a string into various pieces
  with the split being made at the character or
  characters specified as a parameter
• Simple
• apple, banana, peach, orange
• What about
• apple, 0.99, banana, 0.50, peach, 0.25, orange,
  0.75
• Split and retrieve just the names of the fruits
• a-z
• ch8_examp3.htm example

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The replace() Method

• Inserting into a string using replace()
• 1999, 2000, 2001
• To
• the year 1999, the year 2000, the year 2002
• We can refer to groups of character using n
  where n refers to the position of the group
• var myRegExp /\d4/g This finds each group
  of 4 digits
• mystring.replace(myRegExp, the year 1)

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The replace() Method

• Another example
• Replace single quotes with double quotes
• Distinguish single quotes from apostrophe
• Hello World said Mr. OConnerly.
• He then said My Name is OConnerly, yes thats
  right, OConnerly
• // will not work
• /\B\B/g will
• ch8_examp4.htm

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The search() Method

• Allows you to search a string for a pattern of
  characters. If found, return is the position at
  which it was found, else it returns 1
• Finds first occurrence, the /g directive is
  irrelevant
• ch8_examp5.htm

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The match() Method

• Similar to search except it returns an array with
  the matches
• match example 1.htm
• The years were 1999, 2000, and 2001
• Extract just the years
• myRegExp /\bd4\b/g
• A complex example
• ch8_examp5.htm