Modbus crc16 calculation function error syntax

General
1

I used a previous crc16 calculation function, but now it prompts an error syntax. As shown in the picture.

crc16
crc16730×435 17.3 KB 

function crc16(str){
    var buf = Buffer.from(str,'hex')
    var crc = 0xFFFF;
    for(var i = 0;i<buf.length;i++){
        crc = crc^buf[i];
        for(var j = 0;j<8;j++){
            var temp = crc & 0x01;
            crc>>=0x01;
            if(temp == 0x01){
                crc ^= 0xA001;
            }
        }
    }
    return crc;
}

var arr =crc16(msg.payload).toString(16).toUpperCase();
arr = arr.substring(-4).split("");
msg.payload = msg.payload+arr.splice(-2).concat(arr).join("");
return msg;

I temporarily used a simple replacement method, but it doesn't feel strict enough.

msg.payload = Buffer.from(msg.payload + [arr[2]+arr[3]+arr[0]+arr[1]],"hex");

Is there any way to change the error message?Thank you very much!

2

And what is the error message?

3

The error message is：

crc16-02

4

did you mean slice ? there is no splice. There is split and there is slice.

5

declare arr as an array

let arr = [];
arr = crc16(msg.payload).toString(16).toUpperCase();
arr = arr.substring(-4).split("");
msg.payload = msg.payload+arr.splice(-2).concat(arr).join("");
return msg;
6

The issue is monaco (trys) to help too much some times.

It is essentially pointing out the code is not great - the function returns a number, then converts to string then it is split to an array of characters. Technically, it works, but it is ugly.

Here is a very quick fix up...

image

function crc16(str) {
    const buf = Buffer.from(str, 'hex')
    let crc = 0xFFFF;
    for (let i = 0; i < buf.length; i++) {
        crc = crc ^ buf[i];
        for (let j = 0; j < 8; j++) {
            const temp = crc & 0x01;
            crc >>= 0x01;
            if (temp == 0x01) {
                crc ^= 0xA001;
            }
        }
    }
    return crc;
}

const crc = crc16(msg.payload)
const arr = crc.toString(16).toUpperCase().substring(-4).split("")
msg.payload = msg.payload + arr.splice(-2).concat(arr).join("");
return msg;
7

Thank you very much for your prompt reply!

8

This method is also feasible,thank you!