How can I solve this problem using Javascript?

Question

JavaScript

Please tell me the following.
There is a key: 18 and an encrypted message: What is the best way to decrypt it?
Only one way came to my mind.
Are there options to solve this with es6?

Answer 1

It seems that the author wants to see how the function can be rewritten in a more functional style. For example, like this:

function convertText(str, key) {
    key = (26 - key) % 26;

    return [...str].map(symb => {
        const code = symb.charCodeAt(0);
        let shift = 0;

        if ((65 <= code) && (code <= 90)) {
            shift = 65;
        } else if ((97 <= code) && (code <= 122)) {
            shift = 97;
        }
        
        if (shift > 0) {
            return String.fromCharCode(shift + ((code - shift + key) % 26));
        } else {
            return symb;
        }
    }).join('');
}

alert(convertText('Hmjw uzsfuw dwv eq xjawfv Zwjumdw Hgajgl, xgjewjdq uzawx gx lzw Twdyasf xgjuw, lg tw ugffwulwv oalz lzw Klqdwk uskw', 18));