cgode checksum cs *:

cs-gcode.js

// N0 M106*36 
// N1 G28*18 
// N2 M107*39



getCS("N0 M106");
getCS("N1 G28");
getCS("N2 M107");



function getCS(mystr) {
    //https://reprap.org/wiki/G-code#.2A:_Checksum
    var str = toUTF8Array(mystr);
    var cs = 0;
    for (var i = 0; i < str.length; i++) {
       cs = cs ^ str[i];
    }
    cs &= 0xff;
    return cs;
}

function toUTF8Array(str) {
    //https://stackoverflow.com/questions/18729405/how-to-convert-utf8-string-to-byte-array
    var utf8 = [];
    for (var i = 0; i < str.length; i++) {
        var charcode = str.charCodeAt(i);
        if (charcode < 0x80) utf8.push(charcode);
        else if (charcode < 0x800) {
            utf8.push(0xc0 | (charcode >> 6),
                0x80 | (charcode & 0x3f));
        }
        else if (charcode < 0xd800 || charcode >= 0xe000) {
            utf8.push(0xe0 | (charcode >> 12),
                0x80 | ((charcode >> 6) & 0x3f),
                0x80 | (charcode & 0x3f));
        }
        // surrogate pair
        else {
            i++;
            // UTF-16 encodes 0x10000-0x10FFFF by
            // subtracting 0x10000 and splitting the
            // 20 bits of 0x0-0xFFFFF into two halves
            charcode = 0x10000 + (((charcode & 0x3ff) << 10) |
                (str.charCodeAt(i) & 0x3ff));
            utf8.push(0xf0 | (charcode >> 18),
                0x80 | ((charcode >> 12) & 0x3f),
                0x80 | ((charcode >> 6) & 0x3f),
                0x80 | (charcode & 0x3f));
        }
    }
    return utf8;
}