如何使用JavaScript测试字符串中的字母是大写还是小写？

如果字符或整个字符串为数字，则josh和maleki的答案在大写和小写形式上都将返回true。使结果为假结果。使用乔什的例子

var character = '5';if (character == character.toUpperCase()) { alert ('upper case true');}if (character == character.toLowerCase()){ alert ('lower case true');}

另一种方法是先测试它是否为数字，否则测试它是否为大写或小写示例

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++;}