ECA 225 Applied Interactive Programming1 ECA 225 Applied Online Programming strings

ECA 225 Applied Interactive Programming2 this keyword  passes a value to a function based solely on the context of where this is used  can be used to pass entire objects, such as all values submitted through a form

ECA 225 Applied Interactive Programming3 this keyword cont...  compared to function process_form( input ){ var first = input.first_name.value; var last = input.last_name.value; } function process_form( ){ var first = document.myForm.first_name.value; var last = document.myForm.last_name.value; }

ECA 225 Applied Interactive Programming4 String( ) object  creating a String( ) object  a var which has been assigned a string has access to all String properties and methods var greeting = new String( “Hello” ); var greeting = “Hello”;

ECA 225 Applied Interactive Programming5 String( ) properties PropertyDescription lengthreturns the length of the string prototype allows a programmer to add properties to instances of the String( )object  to access a String( ) property use dot notation var greeting = “Hello”; alert( greeting.length );

ECA 225 Applied Interactive Programming6 String( ) methods MethodDescription charAt( ) returns the character at the index passed to the method concat( ) concatenates two passed strings to return a new string indexOf( ) returns the index of the first occurrence of the string passed to the method lastIndexOf( ) returns the index of the last occurrence of the string passed to the method match( ) returns an array containing the matches found based on a regular expression

ECA 225 Applied Interactive Programming7 String( ) methods cont … MethodDescription replace( ) performs a search and replace using a regular expression search( )returns the index location of a match slice( ) returns the string found between the beginning and ending index passed to the method split( )returns the string split into segments substr( ) returns the string beginning with the indexed location and number of characters to return

ECA 225 Applied Interactive Programming8 String( ) methods cont … MethodDescription substring( ) returns the string between the beginning and ending index passed to the method toLowerCase( ) converts all the character in the string to lowercase toString( )returns all passed characters as a string toUpperCase( ) converts all the character in the string to uppercase

ECA 225 Applied Interactive Programming9 String( ) methods cont …  to use a String( )method use dot notation  all methods return a value of some kind  most of the time, what’s returned is some version of the original string  use of String( ) methods do not change the value of the original string  to save what is returned, assign it to a var

ECA 225 Applied Interactive Programming10 string.toUpperCase( )  converts all the characters in the string to uppercase var greeting = “Hello”; var result = greeting.toUpperCase( ); // returns HELLO

ECA 225 Applied Interactive Programming11 string.toLowerCase( )  converts all the characters in the string to lowercase var greeting = “Hello”; var result = greeting.toLowerCase( ); // returns hello

ECA 225 Applied Interactive Programming12 string.indexOf( )  determines if one string is contained by another  index values are zero based  returns the index of the character in the larger string where the smaller string begins  if no match occurs, -1 is returns  to check for a simple match, test whether the returned value is something other than –1  optional 2 nd parameter, the starting index of the search

ECA 225 Applied Interactive Programming13 string.indexOf( ) cont … var greeting = “Hello my Baby.”; var result = greeting.indexOf(“Hello”); alert( greeting ); alert ( result );  change argument to “llo”  change argument to “ool”

ECA 225 Applied Interactive Programming14 string.charAt( )  extracts a single character at a known position  pass the method an index number as an argument  returns the character at the index number var greeting = “Hello my Baby.”; var letter = greeting.charAt( 0 ); alert ( letter );

ECA 225 Applied Interactive Programming15 string.charAt( ) cont …  print the string using  for loop  length property  charAt( ) var greeting = “Hello my Baby.”; for( i=0; i<greeting.length; i++ ){ document.write(greeting.charAt( i )) }

ECA 225 Applied Interactive Programming16 string.substring( ) cont …  extracts a contiguous string of characters  takes 2 parameters  beginning index  ending index ( not part of the substring ) var greeting = “Hello my Baby.”; var result = greeting.substring( 0,4 ); alert( result );

ECA 225 Applied Interactive Programming17 string.substr( ) cont …  extracts a contiguous string of characters  takes 2 parameters  beginning index  length of the substring var greeting = “Hello my Baby.”; var result = greeting.substr( 9,4 ); alert( result );

ECA 225 Applied Interactive Programming18 form validation  form input validation using charAt( ) function valZip( ){ var zip = document.form1.zip.value; if( zip.length != 5 ) { alert( “Invalid zip code") } for( i=0; i 9 ) { alert( “Invalid zip code") } }