如何使用JavaScript测试字符串中的字母是大写还是小写?
当前回答
function isCapital(ch){
return ch.charCodeAt() >= 65 && ch.charCodeAt() <= 90;
}
其他回答
Stephen Nelsons的函数转换成带有大量测试示例的原型。
为了完整起见,我还在函数中添加了整个字符串。
有关其他注释,请参阅代码。
/* Please note, there's no requirement to trim any leading or trailing white spaces. This will remove any digits in the whole string example returning the correct result. */ String.prototype.isUpperCase = function(arg) { var re = new RegExp('\\s*\\d+\\s*', 'g'); if (arg.wholeString) {return this.replace(re, '') == this.replace(re, '').toUpperCase()} else return !!this && this != this.toLocaleLowerCase(); } console.log('\r\nString.prototype.isUpperCase, whole string examples'); console.log(' DDD is ' + ' DDD'.isUpperCase( { wholeString:true } )); console.log('9 is ' + '9'.isUpperCase( { wholeString:true } )); console.log('Aa is ' + 'Aa'.isUpperCase( { wholeString:true } )); console.log('DDD 9 is ' + 'DDD 9'.isUpperCase( { wholeString:true } )); console.log('DDD is ' + 'DDD'.isUpperCase( { wholeString:true } )); console.log('Dll is ' + 'Dll'.isUpperCase( { wholeString:true } )); console.log('ll is ' + 'll'.isUpperCase( { wholeString:true } )); console.log('\r\nString.prototype.isUpperCase, non-whole string examples, will only string on a .charAt(n) basis. Defaults to the first character'); console.log(' DDD is ' + ' DDD'.isUpperCase( { wholeString:false } )); console.log('9 is ' + '9'.isUpperCase( { wholeString:false } )); console.log('Aa is ' + 'Aa'.isUpperCase( { wholeString:false } )); console.log('DDD 9 is ' + 'DDD 9'.isUpperCase( { wholeString:false } )); console.log('DDD is ' + 'DDD'.isUpperCase( { wholeString:false } )); console.log('Dll is ' + 'Dll'.isUpperCase( { wholeString:false } )); console.log('ll is ' + 'll'.isUpperCase( { wholeString:false } )); console.log('\r\nString.prototype.isUpperCase, single character examples'); console.log('BLUE CURAÇAO'.charAt(9) + ' is ' + 'BLUE CURAÇAO'.charAt(9).isUpperCase( { wholeString:false } )); console.log('9 is ' + '9'.isUpperCase( { wholeString:false } )); console.log('_ is ' + '_'.isUpperCase( { wholeString:false } )); console.log('A is ' + 'A'.isUpperCase( { wholeString:false } )); console.log('d is ' + 'd'.isUpperCase( { wholeString:false } )); console.log('E is ' + 'E'.isUpperCase( { wholeString:false } )); console.log('À is ' + 'À'.isUpperCase( { wholeString:false } )); console.log('É is ' + 'É'.isUpperCase( { wholeString:false } )); console.log('Ñ is ' + 'Ñ'.isUpperCase( { wholeString:false } )); console.log('ñ is ' + 'ñ'.isUpperCase( { wholeString:false } )); console.log('Þ is ' + 'Þ'.isUpperCase( { wholeString:false } )); console.log('Ͻ is ' + 'Ͻ'.isUpperCase( { wholeString:false } )); console.log('Ͽ is ' + 'Ͽ'.isUpperCase( { wholeString:false } )); console.log('Ά is ' + 'Ά'.isUpperCase( { wholeString:false } )); console.log('Έ is ' + 'Έ'.isUpperCase( { wholeString:false } )); console.log('ϴ is ' + 'ϴ'.isUpperCase( { wholeString:false } )); console.log('Ϋ is ' + 'Ϋ'.isUpperCase( { wholeString:false } )); console.log('Ϣ is ' + 'Ϣ'.isUpperCase( { wholeString:false } )); console.log('Ϥ is ' + 'Ϥ'.isUpperCase( { wholeString:false } )); console.log('Ϧ is ' + 'Ϧ'.isUpperCase( { wholeString:false } )); console.log('Ϩ is ' + 'Ϩ'.isUpperCase( { wholeString:false } )); console.log('Ϫ is ' + 'Ϫ'.isUpperCase( { wholeString:false } )); console.log('Ϭ is ' + 'Ϭ'.isUpperCase( { wholeString:false } )); console.log('Ϯ is ' + 'Ϯ'.isUpperCase( { wholeString:false } )); console.log('Ϲ is ' + 'Ϲ'.isUpperCase( { wholeString:false } )); console.log('Ϸ is ' + 'Ϸ'.isUpperCase( { wholeString:false } )); console.log('Ϻ is ' + 'Ϻ'.isUpperCase( { wholeString:false } ));
这检查了整个字符串,而不仅仅是第一个字母。我想跟大家分享一下。
下面是一个函数,它使用正则表达式来测试字符串中的字母;如果字母是大写的(A-Z),则返回true。然后我们将true/false数组缩减为单个值。如果它等于字符串的长度,这意味着所有字母都通过了regex测试,这意味着字符串是大写的。如果不是,则字符串为小写。
const isUpperCase = (str) => {
let result = str
.split('')
.map(letter => /[A-Z]/.test(letter))
.reduce((a, b) => a + b);
return result === str.length;
}
console.log(isUpperCase('123')); // false
console.log('123' === '123'.toUpperCase()); // true
josh和maleki的答案如果字符或整个字符串都是数字,则在大写和小写都返回true。使结果为假结果。 使用josh的例子
var character = '5';
if (character == character.toUpperCase()) {
alert ('upper case true');
}
if (character == character.toLowerCase()){
alert ('lower case true');
}
另一种方法是首先测试它是否为数字,否则测试它是否为大写或小写 例子
var strings = 'this iS a TeSt 523 Now!';
var i=0;
var character='';
while (i <= strings.length){
character = strings.charAt(i);
if (!isNaN(character * 1)){
alert('character is numeric');
}else{
if (character == character.toUpperCase()) {
alert ('upper case true');
}
if (character == character.toLowerCase()){
alert ('lower case true');
}
}
i++;
}
function checkCase(c){
var u = c.toUpperCase();
return (c.toLowerCase() === u ? -1 : (c === u ? 1 : 0));
};
根据索尼克·比尔德的评论来主要回答。我改变了结果中的逻辑:
0:小写 1:大写 1:没有
你可以使用正则表达式测试和toUpperCase方法:
String.prototype.charAtIsUpper = function (atpos){
var chr = this.charAt(atpos);
return /[A-Z]|[\u0080-\u024F]/.test(chr) && chr === chr.toUpperCase();
};
// usage (note: character position is zero based)
'hi There'.charAtIsUpper(3); //=> true
'BLUE CURAÇAO'.charAtIsUpper(9); //=> true
'Hello, World!'.charAtIsUpper(5); //=> false
另请参阅