ROT13 (thing)

javascript:P9 = prompt( 'Text...', '' );

if ( P9 ) {
    S2b = '';

    for ( J7 = 0; J7 < P9.length; J7++ ) {
        C6 = P9.charCodeAt( J7 );

        if ( Math.abs( 16 - Math.abs( C6 - 93.5 ) ) <= 13 ) {
            W8b = ( C6 < 91 ) ? 65 : 97;
            S2b += String.fromCharCode(((C6 - W8b + 13) % 26 ) + W8b);
        } else {
            S2b += P9.charAt( J7 );
        }
    }

    alert( S2b );
} else {
    void ( null );
}