JavaScript Reference: Strings

// Two strings:
var firstString = 'Hello world'
var secondString = "nice to meet you"

var newString = String( 6+5+"hello" )
// newString is now the string '11hello'

var firstString = 'Hello world'
var secondString = "nice to meet you"
var message = firstString + " it is " + secondString
console.log(message)

var x = 3, y = 5
var sumString = "The sum of " + x + " and " + y + " is " + (x+y)
console.log(sumString)

length

• Use: Find the length of a string (the number of characters)
• Format: stringName.length
• Example:

  var aString = "Hello world"
  aString.length 	// returns 11 

fromCharCode

• Use: Convert a list of Unicode values to a string
• Format: String.fromCharCode( unicode1, unicode2, ... )
• Example:

  var hiddenMessage = String.fromCharCode(72,69,76,76,79,32,87,79,82,76,68)
  console.log( hiddenMessage ) 

  would result in
  'HELLO WORLD'

anchor

• Use: Create and display HTML anchors
• Format: stringName.anchor( anchorString )
• Example:

  var anchorText = "Section One"
  document.body.innerHTML = anchorText.anchor('section_one_anchor')

  would output the following HTML:
  <a name = "section_one_anchor">Section One</a>

charAt

• Use: Get the character at a particular position in a string
• Format: stringName.charAt( index_value )
• Example:

  var lorem = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." 
  var firstLetter = lorem.charAt(0)
  var tenthLetter = lorem.charAt(9)
  var lastLetter = lorem.charAt(lorem.length - 1)
  console.log( firstLetter, tenthLetter, lastLetter )

  would result in
  L u .
  

charCodeAt

• Use: Get the character's Unicode value at a particular position in a string
• Format: stringName.charCodeAt( index_value )
• Example:

  var lorem = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." 
  var firstLetter = lorem.charCodeAt(0)
  var tenthLetter = lorem.charCodeAt(9)
  var lastLetter = lorem.charCodeAt(lorem.length - 1)
  console.log( firstLetter, tenthLetter, lastLetter )

  would result in
  76 117 46
  

indexOf

• Use: Returns index of first instance of a character (or string) within a string
• Format: stringName.indexOf( 'substring' )
• Example:

  var lorem = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." 
  var firstA = lorem.indexOf('a')
  var firstIp = lorem.indexOf('ip')
  console.log( firstA, firstIp )

  would result in
  22 6

lastIndexOf

• Use: Returns index of last instance of a character (or string) within a string
• Format: stringName.lastIndexOf( 'substring' )
• Example:

  var lorem = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." 
  var lastA = lorem.lastIndexOf('a')
  var lastIp = lorem.lastIndexOf('ip')
  console.log( lastA, lastIp )

  would result in
  122 42

link

• Use: Create and display an HTML link
• Format: stringName.link( url )
• Example:

  var linkText = 'Mercyhurst Math Site'
  var MMurl = 'http://math.mercyhurst.edu'
  document.write( 'Get more information at the ' + linkText.link(MMurl)

  would result in the following text, with link, in the HTML document:
  Get more information at the Mercyhurst Math Site

slice

• Use: Create a new string by extracting a section of an existing string between two indices
• Format: newString = oldString.slice( startIndex, endIndex )
• Example:

  var lorem = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." 
  var loremSubstring = lorem.slice( 6, 17 )
  console.log( loremSubstring )

  would result in
  ipsum dolor
  

substr

• Use: Create a new string by extracting a section of a particular length from an existing string
• Format: newString = oldString.substr( startIndex, lengthOfSubstring )
• Example:

  var lorem = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." 
  var loremSubstring = lorem.substr( 6, 11 )
  console.log( loremSubstring )

  would result in
  ipsum dolor
  

split

• Use: Separate a string into array elements
• Format: arrayName = stringName.split( separator )
• Example:

  var dogString = "labrador,boxer,papillon,chow chow,bulldog"
  var dogArray = dogString.split(",")
  console.log(dogArray)

  would result in
  [ 'labrador', 'boxer', 'papillon', 'chow chow', 'bulldog' ]

toLowerCase

• Use: Convert letters in a string to lower case
• Format: stringName.toLowerCase( )
• Example:

  var myString = "Hello WORLD"
  console.log( myString.toLowerCase() )

  would result in
  hello world

toUpperCase

• Use: Convert letters in a string to upper case
• Format: stringName.toUpperCase( )
• Example:

  var myString = "Hello WORLD"
  console.log( myString.toUpperCase() )

  would result in
  HELLO WORLD

trim

• Use: Remove whitespace from both ends of a string
• Format: stringName.trim( )
• Example:

  var myString = "    Hello WORLD  "
  console.log( myString.toUpperCase() )

  would result in
  Hello WORLD

match

• Use: Returns array with pattern matches or null if match is not found
• Format: stringName.match( pattern )
• Example:

  var lorem = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." 
  var pattern1 = /(in)/g		// find all occurrences of 'in' 
  var result1 = lorem.match(pattern1)
  // result1 = [ 'in', 'in' ]
  var pattern2 = /l\w+/gi		// find all words starting with l, regardless of case	
  var result2 = lorem.match(pattern2)
  // result2 = [ 'Lorem', 'lor', 'lit', 'labore', 'lore', 'liqua' ]

search

• Use: Returns index of first occurrence of pattern in a string
• Format: stringName.search( pattern, 'replacement string' )
• Notes: Use $n to refer to the nth substring
• Example:

  var sampleString = "Hello world!" 
  var pattern = /l/		 
  var result = sampleString.search(pattern)	// find index of first 'l' in string
  result = 2

replace

• Use: Replace a substring by pattern
• Format: stringName.replace( pattern, 'replacement string' )
• Notes: Use $n to refer to the nth substring
• Example:

  var sampleString = "Hello world!" 
  var pattern = /(hello)/i		// find first occurrence of hello, regardless of case 
  var result = sampleString.replace(pattern, 'Goodbye')
  // result = 'Goodbye world!'
  
  var pattern = /l/g				// find all occurrences of 'l' 
  var result = sampleString.replace(pattern, 'k')
  // result = 'Hekko workd!'
  
  var nameString = "John Smith"
  var pattern = /(\w+)\s(\w+)/	// look for pattern word-space-word
  var newNameString = nameString.replace(pattern, '$2, $1')	// second word-comma-first word
  // newNameString = 'Smith, John'