Get Error For Editing Array In Some Condition

Hi All,

I'm trying to create a function to concatenate array data with various conditions. But the result is not what I expected. I've tried issuing node.warn on the variable that outputs several conditions, but there is the following error:

image

Here is the code that I use:

var a = msg.payload[0]; //date
var b = Number(msg.payload[1])/1; //count
var c = msg.payload[2]; //load

var c2={} ;
if ( b < 10){
     c2 = c * 2  ; 
     return c2;
} else if ( 10 < b < 20)
{
    c2 = c *1.5;
    return c2;
} else if ( 20 < b < 30)
{
    c2 = c*1.2;
    return c2;
} else {
    c2 = c;
    return c2;
}

node.warn("c2");


var d = msg.payload[3];
var e = msg.payload[4];
var f = msg.payload[5];
var g = msg.payload[6];

const SENSORS=[a,b,c2,d,e,f,g];
 

msg.payload=SENSORS;

return msg;

Maybe some of you can help me. I really appreciate your help in advance. Thank You

You are returning a number instead of the msg

I suspect you should take out all the return c2 statements.

My Mistakes... Thank you Steve and Colin..