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Core JavaScript Reference 1.5 |
An object representing a series of characters in a string.
JavaScript 1.0: Create a String object only by quoting characters.
JavaScript 1.1, NES 2.0: added String constructor; added prototype property; added split method; added ability to pass strings among scripts in different windows or frames (in previous releases, you had to add an empty string to another window's string to refer to it).
JavaScript 1.2, NES 3.0: added concat, match, replace, search, slice, and substr methods.
JavaScript 1.3: added toSource method; changed charCodeAt, fromCharCode, and replace methods.
Created by
The String constructor:
string
Description
The String object is a wrapper around the string primitive data type. Do not confuse a string literal with the String object. For example, the following code creates the string literal s1 and also the String object s2:s1 = "foo" // creates a string literal value
s2 = new String("foo") // creates a String objectYou can call any of the methods of the String object on a string literal value-JavaScript automatically converts the string literal to a temporary String object, calls the method, then discards the temporary String object. You can also use the String.length property with a string literal.
You should use string literals unless you specifically need to use a String object, because String objects can have counterintuitive behavior. For example:
s1 = "2 + 2" // creates a string literal value
s2 = new String("2 + 2") // creates a String object
eval(s1) // returns the number 4
eval(s2) // returns the string "2 + 2"A string can be represented as a literal enclosed by single or double quotation marks; for example, "Netscape" or `Netscape'.
You can convert the value of any object into a string using the top-level String function.
Property
Description
constructor
length
prototype
Method
Description
anchor
big
Causes a string to be displayed in a big font as if it were in a BIG tag.
blink
bold
charAt
charCodeAt
Returns a number indicating the Unicode value of the character at the given index.
concat
fixed
Causes a string to be displayed in fixed-pitch font as if it were in a TT tag.
fontcolor
Causes a string to be displayed in the specified color as if it were in a <FONT COLOR=color> tag.
fontsize
Causes a string to be displayed in the specified font size as if it were in a <FONT SIZE=size> tag.
fromCharCode
Returns a string created by using the specified sequence of Unicode values. This is a method on the String class, not on a String instance.
indexOf
Returns the index within the calling String object of the first occurrence of the specified value, or -1 if not found.
italics
lastIndexOf
Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found.
link
match
replace
Used to find a match between a regular expression and a string, and to replace the matched substring with a new substring.
search
Executes the search for a match between a regular expression and a specified string.
slice
small
Causes a string to be displayed in a small font, as if it were in a SMALL tag.
split
Splits a String object into an array of strings by separating the string into substrings.
strike
Causes a string to be displayed as struck-out text, as if it were in a STRIKE tag.
sub
Causes a string to be displayed as a subscript, as if it were in a SUB tag.
substr
Returns the characters in a string beginning at the specified location through the specified number of characters.
substring
Returns the characters in a string between two indexes into the string.
sup
Causes a string to be displayed as a superscript, as if it were in a SUP tag.
toLowerCase
toSource
Returns an object literal representing the specified object; you can use this value to create a new object. Overrides the Object.toSource method.
toString
Returns a string representing the specified object. Overrides the Object.toString method.
toUpperCase
valueOf
Returns the primitive value of the specified object. Overrides the Object.valueOf method.
In addition, this object inherits the watch and unwatch methods from Object.
Examples
Example 1: String literal. The following statement creates a string literal:Example 2: String literal properties. The following statements evaluate to 8, "SCHAEFER," and "schaefer":
last_name.length
last_name.toUpperCase()
last_name.toLowerCase()Example 3: Accessing individual characters in a string. You can think of a string as an array of characters. In this way, you can access the individual characters in the string by indexing that array. For example, the following code displays "The first character in the string is H":
var myString = "Hello"
myString[0] // returns "H"Example 4: Pass a string among scripts in different windows or frames. The following code creates two string variables and opens a second window:
var lastName = "Schaefer"
var firstName = "Jesse"
empWindow=window.open('string2.html','window1','width=300,height=300')If the HTML source for the second window (string2.html) creates two string variables, empLastName and empFirstName, the following code in the first window assigns values to the second window's variables:
empWindow.empFirstName=firstName
empWindow.empLastName=lastNameThe following code in the first window displays the values of the second window's variables:
alert('empFirstName in empWindow is ' + empWindow.empFirstName)
alert('empLastName in empWindow is ' + empWindow.empLastName)
Creates an HTML anchor that is used as a hypertext target.
nameAttribute
Description
Use the anchor method with the document.write or document.writeln methods to programmatically create and display an anchor in a document. Create the anchor with the anchor method, and then call write or writeln to display the anchor in a document. In server-side JavaScript, use the write function to display the anchor.In the syntax, the text string represents the literal text that you want the user to see. The nameAttribute string represents the NAME attribute of the A tag.
Anchors created with the anchor method become elements in the document.anchors array.
Examples
The following example opens the msgWindow window and creates an anchor for the table of contents:var myString="Table of Contents"
msgWindow.document.writeln(myString.anchor("contents_anchor"))The previous example produces the same output as the following HTML:
<A NAME="contents_anchor">Table of Contents</A>
See also
String.link
Causes a string to be displayed in a big font as if it were in a BIG tag.
Description
Use the big method with the write or writeln methods to format and display a string in a document. In server-side JavaScript, use the write function to display the string.
Examples
The following example uses string methods to change the size of a string:var worldString="Hello, world"
document.write(worldString.small())
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))The previous example produces the same output as the following HTML:
<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>
See also
String.fontsize, String.small
Causes a string to blink as if it were in a BLINK tag.
Description
Use the blink method with the write or writeln methods to format and display a string in a document. In server-side JavaScript, use the write function to display the string.
Examples
The following example uses string methods to change the formatting of a string:var worldString="Hello, world"
document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())The previous example produces the same output as the following HTML:
<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>
See also
String.bold, String.italics, String.strike
Causes a string to be displayed as bold as if it were in a B tag.
Description
Use the bold method with the write or writeln methods to format and display a string in a document. In server-side JavaScript, use the write function to display the string.
Examples
The following example uses string methods to change the formatting of a string:var worldString="Hello, world"
document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())The previous example produces the same output as the following HTML:
<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>
See also
String.blink, String.italics, String.strike
Returns the specified character from the string.
index
An integer between 0 and 1 less than the length of the string.
Description
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character in a string called stringName is stringName.length - 1. If the index you supply is out of range, JavaScript returns an empty string.
Examples
The following example displays characters at different locations in the string "Brave new world":var anyString="Brave new world"
document.writeln("The character at index 0 is " + anyString.charAt(0))
document.writeln("The character at index 1 is " + anyString.charAt(1))
document.writeln("The character at index 2 is " + anyString.charAt(2))
document.writeln("The character at index 3 is " + anyString.charAt(3))
document.writeln("The character at index 4 is " + anyString.charAt(4))These lines display the following:
The character at index 0 is B
The character at index 1 is r
The character at index 2 is a
The character at index 3 is v
The character at index 4 is e
See also
String.indexOf, String.lastIndexOf, String.split
Returns a number indicating the Unicode value of the character at the given index.
JavaScript 1.3: returns a Unicode value rather than an ISO-Latin-1 value.
index
An integer between 0 and 1 less than the length of the string. The default value is 0.
Description
Unicode values range from 0 to 65,535. The first 128 Unicode values are a direct match of the ASCII character set. For information on Unicode, see the Core JavaScript Guide.JavaScript 1.2. The charCodeAt method returns a number indicating the ISO-Latin-1 codeset value of the character at the given index. The ISO-Latin-1 codeset ranges from 0 to 255. The first 0 to 127 are a direct match of the ASCII character set.
Example
The following example returns 65, the Unicode value for A."ABC".charCodeAt(0) // returns 65
Combines the text of two or more strings and returns a new string.
Syntax
concat(string2, string3[, ..., stringN])
string2...
stringN
Description
concat combines the text from one or more strings and returns a new string. Changes to the text in one string do not affect the other string.
Example
The following example combines two strings into a new string.s1="Oh "
s2="what a beautiful "
s3="mornin'."
s4=s1.concat(s2,s3) // returns "Oh what a beautiful mornin'."
Specifies the function that creates an object's prototype. Note that the value of this property is a reference to the function itself, not a string containing the function's name.
Description
See Object.constructor.
Causes a string to be displayed in fixed-pitch font as if it were in a TT tag.
Description
Use the fixed method with the write or writeln methods to format and display a string in a document. In server-side JavaScript, use the write function to display the string.
Examples
The following example uses the fixed method to change the formatting of a string:var worldString="Hello, world"
document.write(worldString.fixed())The previous example produces the same output as the following HTML:
Causes a string to be displayed in the specified color as if it were in a <FONT COLOR=color> tag.
color
A string expressing the color as a hexadecimal RGB triplet or as a string literal. String literals for color names are listed in the Core JavaScript Guide.
Description
Use the fontcolor method with the write or writeln methods to format and display a string in a document. In server-side JavaScript, use the write function to display the string.If you express color as a hexadecimal RGB triplet, you must use the format rrggbb. For example, the hexadecimal RGB values for salmon are red=FA, green=80, and blue=72, so the RGB triplet for salmon is "FA8072".
The fontcolor method overrides a value set in the fgColor property.
Examples
The following example uses the fontcolor method to change the color of a string:var worldString="Hello, world"
document.write(worldString.fontcolor("maroon") +
" is maroon in this line")
document.write("<P>" + worldString.fontcolor("salmon") +
" is salmon in this line")
document.write("<P>" + worldString.fontcolor("red") +
" is red in this line")document.write("<P>" + worldString.fontcolor("8000") +
" is maroon in hexadecimal in this line")
document.write("<P>" + worldString.fontcolor("FA8072") +
" is salmon in hexadecimal in this line")
document.write("<P>" + worldString.fontcolor("FF00") +
" is red in hexadecimal in this line")The previous example produces the same output as the following HTML:
<FONT COLOR="maroon">Hello, world</FONT> is maroon in this line
<P><FONT COLOR="salmon">Hello, world</FONT> is salmon in this line
<P><FONT COLOR="red">Hello, world</FONT> is red in this line<FONT COLOR="8000">Hello, world</FONT>
is maroon in hexadecimal in this line
<P><FONT COLOR="FA8072">Hello, world</FONT>
is salmon in hexadecimal in this line
<P><FONT COLOR="FF00">Hello, world</FONT>
is red in hexadecimal in this line
Causes a string to be displayed in the specified font size as if it were in a <FONT SIZE=size> tag.
size
An integer between 1 and 7, a string representing a signed integer between 1 and 7.
Description
Use the fontsize method with the write or writeln methods to format and display a string in a document. In server-side JavaScript, use the write function to display the string.When you specify size as an integer, you set the size of stringName to one of the 7 defined sizes. When you specify size as a string such as "-2", you adjust the font size of stringName relative to the size set in the BASEFONT tag.
Examples
The following example uses string methods to change the size of a string:var worldString="Hello, world"
document.write(worldString.small())
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))The previous example produces the same output as the following HTML:
<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>
See also
String.big, String.small
Returns a string created by using the specified sequence of Unicode values.
JavaScript 1.3: uses a Unicode value rather than an ISO-Latin-1 value.
Syntax
fromCharCode(num1, ..., numN)
num1, ..., numN
Description
This method returns a string and not a String object.Because fromCharCode is a static method of String, you always use it as String.fromCharCode(), rather than as a method of a String object you created.
JavaScript 1.2. The fromCharCode method returns a string created by using the specified sequence of ISO-Latin-1 codeset values.
Examples
The following example returns the string "ABC".
Returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex, or -1 if the value is not found.
Syntax
indexOf(searchValue[, fromIndex])
searchValue
fromIndex
The location within the calling string to start the search from. It can be any integer between 0 and the length of the string. The default value is 0.
Description
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character of a string called stringName is stringName.length - 1."Blue Whale".indexOf("Blue") // returns 0
"Blue Whale".indexOf("Blute") // returns -1
"Blue Whale".indexOf("Whale",0) // returns 5
"Blue Whale".indexOf("Whale",5) // returns 5
"Blue Whale".indexOf("",9) // returns 9
"Blue Whale".indexOf("",10) // returns 10
"Blue Whale".indexOf("",11) // returns 10The indexOf method is case sensitive. For example, the following expression returns -1:
Examples
Example 1. The following example uses indexOf and lastIndexOf to locate values in the string "Brave new world."var anyString="Brave new world"
// Displays 8
document.write("<P>The index of the first w from the beginning is " +
anyString.indexOf("w"))
// Displays 10
document.write("<P>The index of the first w from the end is " +
anyString.lastIndexOf("w"))
// Displays 6
document.write("<P>The index of 'new' from the beginning is " +
anyString.indexOf("new"))
// Displays 6
document.write("<P>The index of 'new' from the end is " +
anyString.lastIndexOf("new"))Example 2. The following example defines two string variables. The variables contain the same string except that the second string contains uppercase letters. The first writeln method displays 19. But because the indexOf method is case sensitive, the string "cheddar" is not found in myCapString, so the second writeln method displays -1.
myString="brie, pepper jack, cheddar"
myCapString="Brie, Pepper Jack, Cheddar"
document.writeln('myString.indexOf("cheddar") is ' +
myString.indexOf("cheddar"))
document.writeln('<P>myCapString.indexOf("cheddar") is ' +
myCapString.indexOf("cheddar"))Example 3. The following example sets count to the number of occurrences of the letter x in the string str:
count = 0;
pos = str.indexOf("x");
while ( pos != -1 ) {
count++;
pos = str.indexOf("x",pos+1);
}
See also
String.charAt, String.lastIndexOf, String.split
Causes a string to be italic, as if it were in an <I> tag.
Description
Use the italics method with the write or writeln methods to format and display a string in a document. In server-side JavaScript, use the write function to display the string.
Examples
The following example uses string methods to change the formatting of a string:var worldString="Hello, world"
document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())The previous example produces the same output as the following HTML:
<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>
See also
String.blink, String.bold, String.strike
Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found. The calling string is searched backward, starting at fromIndex.
Syntax
lastIndexOf(searchValue[, fromIndex])
searchValue
fromIndex
The location within the calling string to start the search from. It can be any integer between 0 and the length of the string. The default value is the length of the string.
Description
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character is stringName.length - 1."canal".lastIndexOf("a") // returns 3
"canal".lastIndexOf("a",2) // returns 1
"canal".lastIndexOf("a",0) // returns -1
"canal".lastIndexOf("x") // returns -1The lastIndexOf method is case sensitive. For example, the following expression returns -1:
"Blue Whale, Killer Whale".lastIndexOf("blue")
Examples
The following example uses indexOf and lastIndexOf to locate values in the string "Brave new world."var anyString="Brave new world"
// Displays 8
document.write("<P>The index of the first w from the beginning is " +
anyString.indexOf("w"))
// Displays 10
document.write("<P>The index of the first w from the end is " +
anyString.lastIndexOf("w"))
// Displays 6
document.write("<P>The index of 'new' from the beginning is " +
anyString.indexOf("new"))
// Displays 6
document.write("<P>The index of 'new' from the end is " +
anyString.lastIndexOf("new"))
See also
String.charAt, String.indexOf, String.split
Description
For a null string, length is 0.
Examples
The following example displays 8 in an Alert dialog box:var x="Netscape"
alert("The string length is " + x.length)
Creates an HTML hypertext link that requests another URL.
hrefAttribute
Any string that specifies the HREF attribute of the A tag; it should be a valid URL (relative or absolute).
Description
Use the link method to programmatically create a hypertext link, and then call write or writeln to display the link in a document. In server-side JavaScript, use the write function to display the link.Links created with the link method become elements in the links array of the document object. See document.links.
Examples
The following example displays the word "Netscape" as a hypertext link that returns the user to the Netscape home page:var hotText="Netscape"
var URL="http://home.netscape.com"document.write("Click to return to " + hotText.link(URL))
The previous example produces the same output as the following HTML:
Click to return to <A HREF="http://home.netscape.com">Netscape</A>
Used to match a regular expression against a string.
regexp
Name of the regular expression. It can be a variable name or a literal.
Description
If the regular expression does not include the g flag, returns the same result that RegExp.exec would return on the regular expression and string. If the regular expression includes the g flag, returns an array of all the matches of the regular expression in the string.Note If you execute a match simply to find true or false, use String.search or the regular expression test method.
Examples
Example 1. In the following example, match is used to find 'Chapter' followed by 1 or more numeric characters followed by a decimal point and numeric character 0 or more times. The regular expression includes the i flag so that case will be ignored.<SCRIPT>
str = "For more information, see Chapter 3.4.5.1";
re = /(chapter \d+(\.\d)*)/i;
found = str.match(re);
document.write(found);
</SCRIPT>This returns the array containing Chapter 3.4.5.1,Chapter 3.4.5.1,.1
'Chapter 3.4.5.1' is the first match and the first value remembered from (Chapter \d+(\.\d)*).
'.1' is the second value remembered from (\.\d).
Example 2. The following example demonstrates the use of the global and ignore case flags with match.
<SCRIPT>
str = "abcDdcba";
newArray = str.match(/d/gi);
document.write(newArray);
</SCRIPT>The returned array contains D, d.
Represents the prototype for this class. You can use the prototype to add properties or methods to all instances of a class. For information on prototypes, see Function.prototype.
Finds a match between a regular expression and a string, and replaces the matched substring with a new substring.
JavaScript 1.3: added the ability to specify a function as the second parameter.
Syntax
replace(regexp, newSubStr)
replace(regexp, function)Versions prior to JavaScript 1.3:
regexp
The name of the regular expression. It can be a variable name or a literal.
newSubStr
function
A function to be invoked after the match has been performed.
Description
This method does not change the String object it is called on. It simply returns a new string.If you want to execute a global search and replace, include the g flag in the regular expression.
Specifying a string as a parameter. The replacement string can include the following special replacement patterns:
Specifying a function as a parameter. When you specify a function as the second parameter, the function is invoked after the match has been performed. (The use of a function in this manner is often called a lambda expression.)
In your function, you can dynamically generate the string that replaces the matched substring. The result of the function call is used as the replacement value.
The nested function can use the matched substrings to determine the new string (newSubStr) that replaces the found substring. You get the matched substrings through the parameters of your function. The first parameter of your function holds the complete matched substring. The following n parameters can be used for parenthetical matches, remembered submatch strings, where n is the number of submatch strings in the regular expression. Finally, the last two parameters are the offset within the string where the match occurred and the string itself. For example, the following replace method returns XX.zzzz - XX , zzzz.
"XXzzzz".replace(/(X*)(z*)/,
function (str, p1, p2, offset, s) {
return str + " - " + p1 + " , " + p2;
}
)JavaScript 1.2. You cannot specify a function to be invoked after the match has been performed.
Examples
Example 1. In the following example, the regular expression includes the global and ignore case flags which permits replace to replace each occurrence of 'apples' in the string with 'oranges.'<SCRIPT>
re = /apples/gi;
str = "Apples are round, and apples are juicy.";
newstr=str.replace(re, "oranges");
document.write(newstr)
</SCRIPT>This prints "oranges are round, and oranges are juicy."
Example 2. In the following example, the regular expression is defined in replace and includes the ignore case flag.
<SCRIPT>
str = "Twas the night before Xmas...";
newstr=str.replace(/xmas/i, "Christmas");
document.write(newstr)
</SCRIPT>This prints "Twas the night before Christmas..."
Example 3. The following script switches the words in the string. For the replacement text, the script uses the $1 and $2 replacement patterns.
<SCRIPT LANGUAGE="JavaScript1.2">
re = /(\w+)\s(\w+)/;
str = "John Smith";
newstr = str.replace(re, "$2, $1");
document.write(newstr)
</SCRIPT>Example 4. The following example replaces a Fahrenheit degree with its equivalent Celsius degree. The Fahrenheit degree should be a number ending with F. The function returns the Celsius number ending with C. For example, if the input number is 212F, the function returns 100C. If the number is 0F, the function returns -17.77777777777778C.
The regular expression test checks for any number that ends with F. The number of Fahrenheit degree is accessible to your function through the parameter $1. The function sets the Celsius number based on the Fahrenheit degree passed in a string to the f2c function. f2c then returns the Celsius number. This function approximates Perl's s///e flag.
function f2c(x) {
var s = String(x)
var test = /(\d+(?:\.\d*)?)F\b/g
return s.replace
(test,
function (str,p1,offset,s) {
return ((p1-32) * 5/9) + "C";
}
)
}
Executes the search for a match between a regular expression and this String object.