全角半角处理
c#(转http://www.cnblogs.com/me-sa/articles/759421.html)
A 什么是全角和半角?
(1)全角--指一个字符占用两个标准字符位置。
汉字字符和规定了全角的英文字符及国标GB2312-80中的图形符号和特殊字符都是全角字符。一般的系统命令是不用全角字符的,只是在作文字处理时才会使用全角字符。
(2)半角--指一字符占用一个标准的字符位置。
通常的英文字母、数字键、符号键都是半角的,半角的显示内码都是一个字节。在系统内部,以上三种字符是作为基本代码处理的,所以用户输入命令和参数时一般都使用半角。
B 全角与半角各在什么情况下使用?
全角占两个字节,半角占一个字节。
半角全角主要是针对标点符号来说的,全角标点占两个字节,半角占一个字节,而不管是半角还是全角,汉字都还是要占两个字节。
在编程序的源代码中只能使用半角标点(不包括字符串内部的数据)
在不支持汉字等语言的计算机上只能使用半角标点(其实这种情况根本就不存在半角全角的概念)
对于大多数字体来说,全角看起来比半角大,当然这不是本质区别了。
C 全角和半角的区别
全角就是字母和数字等与汉字占等宽位置的字。半角就是ASCII方式的字符,在没有汉字输入法起做用的时候输入的字母数字和字符都是半角的。
在汉字输入法出现的时候,输入的字母数字默认为半角,但是标点则是默认为全角,可以通过鼠标点击输入法工具条上的相应按钮来改变。
D 关于“全角”和“半角”:
全角:是指中GB2312-80(《信息交换用汉字编码字符集·基本集》)中的各种符号。
半角:是指英文件ASCII码中的各种符号。
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js(转http://www.cnblogs.com/hsapphire/archive/2009/12/18/1627042.html)
一、用JS把全角转换成半角(不能转换标点符号)
<input type="text" size="10" maxlength="10"
onkeyup="javascript:var t = ''; with(this.value) { for (var i = 0; i < length; i++) t += (65296 <= charCodeAt(i) && charCodeAt(i) <= 65305) ? String.fromCharCode(charCodeAt(i) - 65248) : charAt(i); } this.value = t;" />
<br>
<br>
二、用JS把全角转换成半角的函数
<textarea name="n" type="text" id="n" onkeyup="CtoH(this);" style="width:100%;height:100%;"></textarea>
<SCRIPT>
function CtoH(obj){
var str=obj.value;
var result="";
for (var i = 0; i < str.length; i++){
if (str.charCodeAt(i)==12288){
result+= String.fromCharCode(str.charCodeAt(i)-12256);
continue;
}
if (str.charCodeAt(i)>65280 && str.charCodeAt(i)<65375) result+= String.fromCharCode(str.charCodeAt(i)-65248);
else result+= String.fromCharCode(str.charCodeAt(i));
}
obj.value=result;
}
</SCRIPT>
<BR>
<BR>
三、用JS把全角转换成半角(只允许输入数字、小数点与负号)
<input
onkeypress="var k=event.keyCode; return k>=48&&k<=57||k==46||k==45"
onpaste="return !clipboardData.getData('text').match(/\D/)"
ondragenter="return false" style="ime-mode:Disabled"
>
<br>
<br>
四、用JS把全角转换成半角(只允许输入数字)
<input
onkeypress="var k=event.keyCode; return k>=48&&k<=57"
onpaste="return !clipboardData.getData('text').match(/\D/)"
ondragenter="return false" style="ime-mode:Disabled"
>
<br><br>
五、不允许输入全角字符
<INPUT name="CardId" onKeyUp="quanjiao(this);">
<script language="javascript">
function quanjiao(obj){
var str=obj.value;
if (str.length>0){
for (var i = str.length-1; i >= 0; i--){
unicode=str.charCodeAt(i);
if (unicode>65280 && unicode<65375){
alert("不能输入全角字符,请输入半角字符");
obj.value=str.substr(0,i);
}
}
}
}
<input type="text" size="10" maxlength="10"
onkeyup="javascript:var t = ''; with(this.value) { for (var i = 0; i < length; i++) t += (65296 <= charCodeAt(i) && charCodeAt(i) <= 65305) ? String.fromCharCode(charCodeAt(i) - 65248) : charAt(i); } this.value = t;" />
<br>
<br>
二、用JS把全角转换成半角的函数
<textarea name="n" type="text" id="n" onkeyup="CtoH(this);" style="width:100%;height:100%;"></textarea>
<SCRIPT>
function CtoH(obj){
var str=obj.value;
var result="";
for (var i = 0; i < str.length; i++){
if (str.charCodeAt(i)==12288){
result+= String.fromCharCode(str.charCodeAt(i)-12256);
continue;
}
if (str.charCodeAt(i)>65280 && str.charCodeAt(i)<65375) result+= String.fromCharCode(str.charCodeAt(i)-65248);
else result+= String.fromCharCode(str.charCodeAt(i));
}
obj.value=result;
}
</SCRIPT>
<BR>
<BR>
三、用JS把全角转换成半角(只允许输入数字、小数点与负号)
<input
onkeypress="var k=event.keyCode; return k>=48&&k<=57||k==46||k==45"
onpaste="return !clipboardData.getData('text').match(/\D/)"
ondragenter="return false" style="ime-mode:Disabled"
>
<br>
<br>
四、用JS把全角转换成半角(只允许输入数字)
<input
onkeypress="var k=event.keyCode; return k>=48&&k<=57"
onpaste="return !clipboardData.getData('text').match(/\D/)"
ondragenter="return false" style="ime-mode:Disabled"
>
<br><br>
五、不允许输入全角字符
<INPUT name="CardId" onKeyUp="quanjiao(this);">
<script language="javascript">
function quanjiao(obj){
var str=obj.value;
if (str.length>0){
for (var i = str.length-1; i >= 0; i--){
unicode=str.charCodeAt(i);
if (unicode>65280 && unicode<65375){
alert("不能输入全角字符,请输入半角字符");
obj.value=str.substr(0,i);
}
}
}
}