stringConverter

gistfile1.js

/*
function takes 3 parameters:
str - string to convert
state - case "up" = uppercase, "low" = lowercase 
invert(optional) - if true, the first letter will be oposite case    
*/
function convertString(str, state, invert) {
    let result = '';
    switch (state) {
        case 'low':
        for (let i = 0; i < str.length; i++) {
           result+=toLower(str[i])
        }
        if(invert){
            result = toUpper(str[0]) + result.slice(1)
        }
            break;
        case 'up':
        for (let i = 0; i < str.length; i++) {
           result +=toUpper(str[i])
        }
        if(invert){
            result = toLower(str[0]) + result.slice(1)
        }
            break;
        default:
            result = 'invalid arguments'
            break;
    }
    return result;
}

function toUpper(char){
    if( char.codePointAt() >= 97 && char.codePointAt() <= 122 ){ // asci range for lowercase characters
       return String.fromCodePoint(char.codePointAt() - 32)
    }
    if( char.codePointAt() >= 1072 && char.codePointAt() <= 1103 ){// acsi range for lower cyrillic characters except 'ё'
        return String.fromCodePoint(char.codePointAt() - 32)   
    }
    return char;
}

function toLower(char){
    if( char.codePointAt() >= 65  && char.codePointAt() <= 90 ){ // asci range for uppercase characters
        return String.fromCodePoint(char.codePointAt()+ 32)
     
    }
    if( char.codePointAt() >= 1040  && char.codePointAt() <= 1071 ){ // acsi range for  uppercase cyrillic characters except 'Ё'
        return String.fromCodePoint(char.codePointAt()+ 32)
        
    }
    return char;
}

console.log(convertString('Hello', 'up', true));
console.log(convertString('Привет', 'up', true));
console.log(convertString('КАПС ОФФ', 'low'));

Все ок, но Ё не работает))