ESP8266 home controller

Sorry if this isn't the right place, hoping this thread is for general development using the ESP8266.

I've been learning Javascript the last few days and have got these functions written. While we can do most of this stuff in C/C++, some things are easier to accomplish in Javascript like string parsing. My thought is to do as much as I can with Javascript and then send a completed command to the ESP to send out.

// CRC function for 9X commands
function crc(values){
    var checksum = 0, byteIndex = 0, bitLength;
    var byteLength = values[0] - 0x8F;
    do {
        checksum ^= values[byteIndex];
        bitLength = 7;
        do {
            if (checksum & 1) checksum = checksum >> 1 ^ 0x8C;
            else checksum >>= 1;
        } while (bitLength--);
        byteIndex++;
    } while(byteLength--);
    return checksum;
}
// Removes non-hex characters and spaces from a string.
function stripNonHex(hexstr){
    return hexstr.replace(/[^A-F0-9]/gi, "");
}
// Testing to make sure CRC works
function testCRC(){
    // Grab line from text box named "input" on page and strip out non-hex characters and spaces.
    var command = stripNonHex(document.getElementById("input").value);
    // Split string into string array every two characters.
    command = command.match(/[\s\S]{1,2}/g) || [];
    // Create array and create a view using unsigned bytes.
    var commandByteView = new Uint8Array(new ArrayBuffer(command.length+2));
    // Set the length byte based on the number of hex strings.
    commandByteView[0] = command.length + 0x8F;
    // Convert each hex string to a integer
    for(index = 0; index < command.length; index++){
        commandByteView[index+1] = (parseInt(command[index], 16));
    }
    // Calculate CRC and add to end of array.
    commandByteView[command.length + 1] = crc(commandByteView);
    // Print to log the complete command in decimal and hex string form.
    var outputString = "";
    for(index = 0; index < commandByteView[0] - 0x8D; index++){
        // Convert from int to hex
        var temp = commandByteView[index].toString(16);
        // Zero padding or zero-fill for values > 0x10 and using uppercase hex
        temp = ('0' + temp).slice(-2).toUpperCase();
        outputString += temp + " ";
    }
    console.log("DEC View: " + commandByteView);
    console.log("HEX View: " + outputString);
}

I agree on the web pages being good for presentations of our individual projects. We can continue to tack on updates, notes, and changes as we need them. Kind of like writing an article, I guess? We present things differently when it's a forum post vs. an article.

JSON is one of those things that while I like the format of it, the libraries of non-Javascript languages are spotty at best. I was having issues with one library outputting a JSON array because it was possible to include malicious code. While we can move bits and pieces client side, there's some stuff that should be kept server side. Things like playing a show should be kept server side for correct timing. However, once string parsing and some other settings are set up there's no reason we can't transfer control back to the server. When I was first looking at things I wanted to keep as much server side as I could, we have a whole 1024 KB for server side code. While on the client side, things are programmed in text which takes up a lot more space. However, we have space. As much as I want to optimize things to be tiny I have to remember, we have space. Even Don's index.htm where he keeps all of the HTML, CSS, and JS is only 7.7KB, that's 0.25% of the SPIFFS flash.

I didn't even know there was issues with JS on different browsers, I thought that was mostly CSS that had issues. The more you know. Actually now that I think about it there's different JS engines so that makes total sense. The reason I even thought about using JS for some of this was with string parsing. It's really clumsy doing it yourself, even my own C code to work through it is specific and does some lazy things. 

The only library I was looking at using was Snap.svg and that's 27KB pre-gzip. Does the ESP Webserver even support gzip? As I'm poking around at jQuery info, there's also dependencies that I remember being mentioned. For me, I want things to be as self-contained as possible. Webdev is a whole new world 🎶 for me and I'm sure most of us; so much to explore and learn.

I've been developing using JS in a separate file but I can see the issue with the client caching it and not getting the updates, crossing that bridge when we get to it.

On the 9X length value, I have code for it above, just rolled into the testCRC function. I was getting lazy about abstracting it out at that point. It's just a matter of counting the number of parsed two letter hex digits and adding it to the front of the array.

Anyways, got home a few hours ago and a nap seemed more important than coding at the time. Maybe I'll find some dinner and get some coding done. I need to figure out this CSS thing and probably actually learn HTML properly.