check if letter is uppercase javascript

1function isUpper(str) {
2    return !/[a-z]/.test(str) && /[A-Z]/.test(str);
3}
4
5isUpper("FOO"); //true
6isUpper("bar"); //false
7isUpper("123"); //false
8isUpper("123a"); //false
9isUpper("123A"); //true
10isUpper("A123"); //true
11isUpper(""); //false
12

1const isUpperCase = (string) => /^[A-Z]*$/.test(string)
2

1var regex = /^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])(?=.*[!#\*\?])(?=.{8,})/;

1isUpperCase('A') // true
2isUpperCase('a') // false
3

1var strings = 'this iS a TeSt 523 Now!';
2var i=0;
3var character='';
4while (i <= strings.length){
5    character = strings.charAt(i);
6    if (!isNaN(character * 1)){
7        alert('character is numeric');
8    }else{
9        if (character == character.toUpperCase()) {
10            alert ('upper case true');
11        }
12        if (character == character.toLowerCase()){
13            alert ('lower case true');
14        }
15    }
16    i++;
17}
18

1var str = S;
2
3  if (str == str.toUpperCase())
4  {
5    console.log(" Uppercase");
6  }
7  else
8  {
9    console.log("Lowercase");
10  }