JavaScript中String物件常見方法及屬性
JavaScript String物件簡介
在JavaScript,基本資料型別有Number型、String型、Boolean型、Undefined型、Null型、Function型等。
String物件就是和基本資料型別中的String型別相對應的JavaScript指令碼內建物件。(熟悉Java的話,可以類比Java基本資料型別和基本資料型別封裝類的概念。)
在JavaScript指令碼程式中,String物件十分常見。JavaScript提供了豐富的屬性、方法支援,便於靈活高效地操作String物件。
獲取String物件例項
var MyStr = new String(); var MyStr = new String(str);
str
為可選引數,用來對String物件進行初始化。
JavaScript String物件常用方法、屬性
1、length屬性
length屬性儲存目標字串所包含的字元數,為只讀屬性。示例:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringLength() {
var MyString = new String("Hello World!");
var msg = "The length of string is : " ;
msg += MyString.length;
alert(msg);
}
-->
</script>
輸出:
The length of string is : 12
2、小寫轉換toLowerCase()
toLowerCase()方法可以將字串中的大寫字母全部轉換為對應的小寫字母,示例:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod () {
var MyString = new String("Hello World!");
MyString = MyString.toLowerCase();
alert(MyString);
}
-->
</script>
輸出:
hello world!
3、大寫轉換toUpperCase()
將字串中所有小寫字母轉換為對應的大寫字母,示例:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World!");
MyString = MyString.toUpperCase();
alert(MyString);
}
-->
</script>
輸出:
HELLO WORLD!
4、字串替換replace()
replace(regexp/substr, replacement)方法將regexp/substr處的正則或字串直接量替換為replacement,示例:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World!");
MyString = MyString.replace("World", "Beijing");
alert(MyString);
}
-->
</script>
輸出:
Hello Beijing!
5、字串匹配match()
match(str)方法在字串中查詢str所指定的字串,若查詢成功,返回該字串,否則返回null。str可以作為一個表示式。示例:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World!");
MyString = MyString.match("He" + "llo");
var MyString1 = new String("Hello Beijing");
MyString1 = MyString1.match("Wu");
alert(MyString + "\n" + MyString1);
}
-->
</script>
輸出:
Hello
null
6、字串拼接concat()
MyString.concat(str)方法將str串連線到MyString字串後。可以同時依次連線多個字串如MyString.concat(str1, str2, str3)。示例:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World!");
MyString = MyString.concat(" ", "This is", " a nice world!");
alert(MyString);
}
-->
</script>
輸出:
Hello World! This is a nice world!
7、字串分割split()
split()方法用於將字串分割,split(str, num)以str為指定分割符,返回分割的num個子串陣列。例如:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World! This is a nice world!");
subArray = MyString.split(" ", 3);
var msg = " ";
for(var i = 0; i < subArray.length; i ++) {
msg += subArray[i];
msg += "\n"
}
alert(msg);
}
-->
</script>
輸出:
Hello
World!
This
如果不指定split(str, num)中的num,則會返回分割後所有子串陣列:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World! This is a nice world!");
subArray = MyString.split(" ");
var msg = " ";
for(var i = 0; i < subArray.length; i ++) {
msg += subArray[i];
msg += "\n"
}
alert(msg);
}
-->
</script>
輸出:
Hello
World!
This
is
a
nice
world!
8、字串檢索indexOf()
indexOf(str, s)方法,在字串中檢索str出現的位置,s為可選引數,指定檢索開始的位置。s的合法取值範圍為0~String.length-1。若檢索成功,則返回匹配子串的首字母下標,否則返回-1。示例:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World! This is a nice world!");
var index = MyString.indexOf("World");
alert(index);
}
-->
</script>
輸出:
6
若指定s位置為7,則會返回-1:
<script language="JavaScript" content="text/JavaScript";>
<!--
function StringMethod() {
var MyString = new String("Hello World! This is a nice world!");
var index = MyString.indexOf("World", 7);
alert(index);
}
-->
</script>
輸出:
-1
特別注意
以上對字串操作的方法,並沒有直接操作字串本身,而是返回操作後的結果。例如:
var MyString = new String("Hello World!");
MyString.concat("Beijing");
此時列印MyString的值,依然是Hello World!
。若要改變字串本身,需要將返回的結果對字串進行賦值:
var MyString = new String("Hello World!");
MyString = MyString.concat("Beijing");
這樣打印出MyString即為Hello World!Beijing
。