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String

An object representing a series of characters in a string.

Core object
实现版本 Navigator 2.0: Create a String object only by quoting characters.
Navigator 3.0, LiveWire 1.0: 添加了 String constructor; 添加了 prototype 属性; 添加了 split 方法; 添加了 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)
Navigator 4.0, Netscape Server 3.0: 添加了 concat, match, replace, search, slice, and substr 方法s.

方法概览

示例

示例 1: String variable. The following statement creates a string variable:

var last_name = "Schaefer" 示例 2: String object properties. The following statements evaluate to 8, "SCHAEFER," and "schaefer":

last_name.length
last_name.toUpperCase()
last_name.toLowerCase() 示例 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:

var myString = "Hello"
document.write ("The first character in the string is " + myString[0]) displays "The first character in the string is H"

示例 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 = new String("Schaefer")
var firstName = new String ("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=lastName The 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)

length

The length of the string.

属性源 String
只读
实现版本 Navigator 2.0, LiveWire 1.0

示例

The following example displays 8 in an Alert dialog box:

var x="Netscape"
alert("The string length is " + x.length)

prototype

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.

属性源 String
实现版本 Navigator 3.0, Netscape Server 3.0

anchor

Creates an HTML anchor that is used as a hypertext target.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

参数

nameAttribute A string.

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语法, 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.

示例

The following example opens the msgWindow window and creates an anchor for the 表 of contents:

var myString="表 of Contents"
msgWindow.document.writeln(myString.anchor("contents_anchor")) The previous example produces the same output as the following HTML:

<A NAME="contents_anchor">表 of Contents</A> In server-side JavaScript, you can generate this HTML by calling the write function instead of using document.writeln.

参看

String.link

big

Causes a string to be displayed in a big font as if it were in a BIG tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

big()

参数

无

描述

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.

示例

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>

参看

String.fontsize, String.small

blink

Causes a string to blink as if it were in a BLINK tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

blink()

参数

无

描述

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.

示例

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>

参看

String.bold, String.italics, String.strike

bold

Causes a string to be displayed as bold as if it were in a B tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

bold()

参数

无

描述

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.

示例

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>

参看

String.blink, String.italics, String.strike

charAt

Returns the specified character from the string.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

charAt(index)

参数

index An integer between 0 and 1 less than the length of the string.

描述

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.

示例

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

In server-side JavaScript, you can display the same output by calling the write function instead of using document.write.

参看

String.indexOf, String.lastIndexOf, String.split

charCodeAt

Returns a number indicating the ISO-Latin-1 codeset value of the character at the given index.

方法源 String
实现版本 Navigator 4.0, Netscape Server 3.0

语法

charCodeAt(index)

参数

index (Optional) An integer between 0 and 1 less than the length of the string. The default value is 0.

描述

The ISO-Latin-1 codeset ranges from 0 to 255. The first 0 to 127 are a direct match of the ASCII character set.

示例

The following example returns 65, the ISO-Latin-1 codeset value for A.

"ABC".charCodeAt(0)

concat

Combines the text of two strings and returns a new string.

方法源 String
实现版本 Navigator 4.0, Netscape Server 3.0

语法

concat(string2)

参数

string1 The first string.
string2 The second string.

描述

concat combines the text from two strings and returns a new string. Changes to the text in one string do not affect the other string.

示例

The following example combines two strings into a new string.

<SCRIPT>
str1="The morning is upon us. "
str2="The sun is bright."
str3=str1.concat(str2)
document.writeln(str1)
document.writeln(str2)
document.writeln(str3)
</SCRIPT> This writes:

The morning is upon us.
The sun is bright.
The morning is upon us. The sun is bright.

fixed

Causes a string to be displayed in fixed-pitch font as if it were in a TT tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

fixed()

参数

无

描述

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.

示例

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:

<TT>Hello, world</TT>

fontcolor

Causes a string to be displayed in the specified color as if it were in a <FONT COLOR=color> tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

fontcolor(color)

参数

color A string expressing the color as a hexadecimal RGB triplet or as a string literal. String literals for color names are listed in Appendix B, "Color Values," in the JavaScript Guide.

描述

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.

示例

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

fromCharCode

Returns a string created by using the specified sequence ISO-Latin-1 codeset values.

方法源 String
静态
实现版本 Navigator 4.0, Netscape Server 3.0

语法

fromCharCode(num1, ..., numN)

参数

num1, ..., numN A sequence of numbers that are ISO-Latin-1 codeset values.

描述

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.

示例

示例 1. The following example returns the string "ABC".

String.fromCharCode(65,66,67) 示例 2. The which property of the KeyDown, KeyPress, and KeyUp events contains the ASCII value of the key pressed at the time the event occurred. If you want to get the actual letter, number, or symbol of the key, you can use fromCharCode. The following example returns the letter, number, or symbol of the KeyPress event's which property.

String.fromCharCode(KeyPress.which)

indexOf

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.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

indexOf(searchValue, fromIndex)

参数

searchValue A string representing the value to search for.
fromIndex (Optional) The location within the calling string to start the search from. It can be any integer between 0 and 1 less than the length of the string. The default value is 0.

描述

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.

If stringName contains an empty string (""), indexOf returns an empty string.

The indexOf method is case sensitive. For example, the following expression returns -1:

"Blue Whale".indexOf("blue")

示例

示例 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")) 示例 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")) 示例 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);
}

参看

String.charAt, String.lastIndexOf, String.split

italics

Causes a string to be italic, as if it were in an I tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

italics()

参数

无

描述

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.

示例

The following example uses string methods to change the formatting of a string:

<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>

参看

String.blink, String.bold, String.strike

lastIndexOf

Returns the index within the calling String object of the last occurrence of the specified value. The calling string is searched backward, starting at fromIndex, or -1 if not found.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

lastIndexOf(searchValue, fromIndex)

参数

描述

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.

The lastIndexOf method is case sensitive. For example, the following expression returns -1:

"Blue Whale, Killer Whale".lastIndexOf("blue")

示例

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")) In server-side JavaScript, you can display the same output by calling the write function instead of using document.write.

参看

String.charAt, String.indexOf, String.split

link

Creates an HTML hypertext link that requests another URL.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

link(hrefAttribute)

参数

hrefAttribute Any string that specifies the HREF attribute of the A tag; it should be a valid URL (relative or absolute).

描述

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.

示例

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>

参看

Anchor

match

Used to match a regular expression against a string.

方法源 String
实现版本 Navigator 4.0

语法

match(regexp)

参数

regexp Name of the regular expression. It can be a variable name or a literal.

描述

If you want to execute a global match, or a case insensitive match, include the g (for global) and i (for ignore case) flags in the regular expression. These can be included separately or together. The following two示例 below show how to use these flags with match.

Note

If you execute a match simply to find true or false, use String.search or the regular expression test method.

示例

示例 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).

示例 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.

replace

Used to find a match between a regular expression and a string, and to replace the matched substring with a new substring.

方法源 String
实现版本 Navigator 4.0

语法

replace(regexp, newSubStr)

参数

regexp The name of the regular expression. It can be a variable name or a literal.
newSubStr The string to put in place of the string found with regexp. This string can include the RegExp properties $1, ..., $9, lastMatch, lastParen, leftContext, and rightContext.

描述

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, or a case insensitive search, include the g (for global) and i (for ignore case) flags in the regular expression. These can be included separately or together. The following two示例 below show how to use these flags with replace.

示例

示例 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."

示例 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..."

示例 3. The following script switches the words in the string. For the replacement text, the script uses the values of the $1 and $2 properties.

<SCRIPT LANGUAGE="JavaScript1.2">
re = /(\w+)\s(\w+)/;
str = "John Smith";
newstr = str.replace(re, "$2, $1");
document.write(newstr)
</SCRIPT> This prints "Smith, John".

search

Executes the search for a match between a regular expression and this String object.

方法源 String
实现版本 Navigator 4.0

语法

search(regexp)

参数

regexp Name of the regular expression. It can be a variable name or a literal.

描述

If successful, search returns the index of the regular expression inside the string. Otherwise, it returns -1.

When you want to know whether a pattern is found in a string use search (similar to the regular expression test method); for more information (but slower execution) use match (similar to the regular expression exec method).

示例

The following example prints a message which depends on the success of the test.

function testinput(re, str){
   if (str.search(re) != -1)
      midstring = " contains ";
   else
      midstring = " does not contain ";
   document.write (str + midstring + re.source);
}

slice

Extracts a section of a string and returns a new string.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

slice(beginslice,endSlice)

参数

beginSlice The zero-based index at which to begin extraction.
endSlice (Optional) The zero-based index at which to end extraction. If omitted, slice extracts to the end of the string.

描述

slice extracts the text from one string and returns a new string. Changes to the text in one string do not affect the other string.

slice extracts up to but not including endSlice. string.slice(1,4) extracts the second character through the fourth character (characters indexed 1, 2, and 3).

As a negative index, endSlice indicates an offset from the end of the string. string.slice(2,-1) extracts the third character through the second to last character in the string.

示例

The following example uses slice to create a new string.

<SCRIPT>
str1="The morning is upon us. "
str2=str1.slice(3,-5)
document.write(str2)
</SCRIPT> This writes:

morning is upon

small

Causes a string to be displayed in a small font, as if it were in a SMALL tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

small()

参数

无

描述

Use the small 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.

示例

The following example uses string methods to change the size of a string:

<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>

参看

String.big, String.fontsize

split

Splits a String object into an array of strings by separating the string into substrings.

方法源 String
实现版本 Navigator 3.0, LiveWire 1.0

语法

split(separator, limit)

参数

separator (Optional) Specifies the character to use for separating the string. The separator is treated as a string. If separator is omitted, the array returned contains one element consisting of the entire string.
limit (Optional) Integer specifying a limit on the number of splits to be found.

描述

The split method returns the new array.

When found, separator is removed from the string and the substrings are returned in an array. If separator is omitted, the array contains one element consisting of the entire string.

In Navigator 4.0, Split has the following additions:

It can take a regular expression argument, as well as a fixed string, by which to split the object string. If separator is a regular expression, any included parenthesis cause submatches to be included in the returned array.

It can take a limit count so that it won't include trailing empty elements in the resulting array.

If you specify LANGUAGE="JavaScript1.2" in the SCRIPT tag, string.split(" ") splits on any run of 1 or more white space characters including spaces, tabs, line feeds, and carriage returns.

示例

示例 1. The following example defines a function that splits a string into an array of strings using the specified separator. After splitting the string, the function displays messages indicating the original string (before the split), the separator used, the number of elements in the array, and the individual array elements.

function splitString (stringToSplit,separator) {
   arrayOfStrings = stringToSplit.split(separator)
   document.write ('<P>The original string is: "' + stringToSplit + '"')
   document.write ('<BR>The separator is: "' + separator + '"')
   document.write ("<BR>The array has " + arrayOfStrings.length + " elements: ")    for (var i=0; i < arrayOfStrings.length; i++) {
      document.write (arrayOfStrings[i] + " / ")
   }
} var tempestString="Oh brave new world that has such people in it."
var monthString="Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec" var space=" "
var comma="," splitString(tempestString,space)
splitString(tempestString)
splitString(monthString,comma) This example produces the following output:

The original string is: "Oh brave new world that has such people in it."
The separator is: " "
The array has 10 elements: Oh / brave / new / world / that / has / such / people / in / it. / The original string is: "Oh brave new world that has such people in it."
The separator is: "undefined"
The array has 1 elements: Oh brave new world that has such people in it. / The original string is: "Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec"
The separator is: ","
The array has 12 elements: Jan / Feb / Mar / Apr / May / Jun / Jul / Aug / Sep / Oct / Nov / Dec / 示例 2. Consider the following script:

<SCRIPT LANGUAGE="JavaScript1.2">
str="She sells seashells \nby the\n seashore"
document.write(str + "<BR>")
a=str.split(" ")
document.write(a)
</SCRIPT> Using LANGUAGE="JavaScript1.2", this script produces

"She", "sells", "seashells", "by", "the", "seashore" Without LANGUAGE="JavaScript1.2", this script splits only on single space characters, producing

"She", "sells", , , , "seashells", "by", , , "the", "seashore" 示例 3. In the following example, split looks for 0 or more spaces followed by a semicolon followed by 0 or more spaces and, when found, removes the spaces from the string. nameList is the array returned as a result of split.

<SCRIPT>
names = "Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ;Chris Hand ";
document.write (names + "<BR>" + "<BR>");
re = /\s*;\s*/;
nameList = names.split (re);
document.write(nameList);
</SCRIPT> This prints two lines; the first line prints the original string, and the second line prints the resulting array.

Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ;Chris Hand
Harry Trump,Fred Barney,Helen Rigby,Bill Abel,Chris Hand

示例 4. In the following example, split looks for 0 or more spaces in a string and returns the first 3 splits that it finds.

<SCRIPT LANGUAGE="JavaScript1.2">
myVar = " Hello World. How are you doing? ";
splits = myVar.split(" ", 3);
document.write(splits)
</SCRIPT> This script displays the following:

["Hello", "World.", "How"]

参看

String.charAt, String.indexOf, String.lastIndexOf

strike

Causes a string to be displayed as struck-out text, as if it were in a STRIKE tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

strike()

参数

无

描述

Use the strike 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.

示例

The following example uses string methods to change the formatting of a string:

<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>

参看

String.blink, String.bold, String.italics

sub

Causes a string to be displayed as a subscript, as if it were in a SUB tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

sub()

参数

无

描述

Use the sub 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 generate the HTML.

示例

The following example uses the sub and sup methods to format a string:

var superText="superscript"
var subText="subscript" document.write("This is what a " + superText.sup() + " looks like.")
document.write("<P>This is what a " + subText.sub() + " looks like.") The previous example produces the same output as the following HTML:

This is what a <SUP>superscript</SUP> looks like.
<P>This is what a <SUB>subscript</SUB> looks like.

参看

String.sup

substr

Returns the characters in a string beginning at the specified location through the specified number of characters.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

substr(start, length)

参数

start Location at which to begin extracting characters.
length (Optional) The number of characters to extract

描述

start is a character index. The index of the first character is 0, and the index of the last character is 1 less than the length of the string. substr begins extracting characters at start and collects length number of characters.

If start is positive and is the length of the string or longer, substr returns no characters.

If start is negative, substr uses it as a character index from the end of the string. If start is negative and abs(start) is larger than the length of the string, substr uses 0 is the start index.

If length is 0 or negative, substr returns no characters. If length is omitted, start extracts characters to the end of the string.

示例

Consider the following script:

<SCRIPT LANGUAGE="JavaScript1.2"> str = "abcdefghij"
document.writeln("(1,2): ", str.substr(1,2))
document.writeln("(-2,2): ", str.substr(-2,2))
document.writeln("(1): ", str.substr(1))
document.writeln("(-20, 2): ", str.substr(1,20))
document.writeln("(20, 2): ", str.substr(20,2)) </SCRIPT> This script displays:

(1,2): bc
(-2,2): ij
(1): bcdefghij
(-20, 2): bcdefghij
(20, 2):

参看

substring

Returns a subset of a String object.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

substring(indexA, indexB)

参数

indexA An integer between 0 and 1 less than the length of the string.
indexB An integer between 0 and 1 less than the length of the string.

描述

substring extracts characters from indexA up to but not including indexB. In particular:

If indexA is less than 0, indexA is treated as if it were 0.

If indexB is greater than stringName.length, indexB is treated as if it were stringName.length.

If indexA equals indexB, substring returns an empty string.

If indexB is omitted, indexA extracts characters to the end of the string.

Using LANGUAGE="JavaScript1.2" in the SCRIPT tag,

If indexA is greater than indexB, JavaScript produces a runtime error (out of memory).

Without LANGUAGE="JavaScript1.2",

If indexA is greater than indexB, JavaScript returns a substring beginning with indexB and ending with indexA - 1.

示例

示例 1. The following example uses substring to display characters from the string "Netscape":

var anyString="Netscape" //Displays "Net"
document.write(anyString.substring(0,3))
document.write(anyString.substring(3,0))
//Displays "cap"
document.write(anyString.substring(4,7))
document.write(anyString.substring(7,4))
//Displays "Netscap"
document.write(anyString.substring(0,7))
//Displays "Netscape"
document.write(anyString.substring(0,8))
document.write(anyString.substring(0,10)) 示例 2. The following example replaces a substring within a string. It will replace both individual characters and substrings. The function call at the end of the example changes the string "Brave New World" into "Brave New Web".

function replaceString(oldS,newS,fullS) {
// Replaces oldS with newS in the string fullS
   for (var i=0; i<fullS.length; i++) {
      if (fullS.substring(i,i+oldS.length) == oldS) {
         fullS = fullS.substring(0,i)+newS+fullS.substring(i+oldS.length,fullS.length)
      }
   }
   return fullS
} replaceString("World","Web","Brave New World") 示例 3. Using LANGUAGE="JavaScript1.2", the following script produces a runtime error (out of memory).

<SCRIPT LANGUAGE="JavaScript1.2">
str="Netscape"
document.write(str.substring(0,3);
document.write(str.substring(3,0);
</SCRIPT> Without LANGUAGE="JavaScript1.2", the above script prints

Net Net

In the second write, the index numbers are swapped.

参看

substr

sup

Causes a string to be displayed as a superscript, as if it were in a SUP tag.

方法源 String
实现版本 Navigator 2.0, LiveWire 1.0

语法

sup()

参数

无

描述

Use the sup 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 generate the HTML.