Function: convert Messages to array

General
1

Hello guys,
I want to create as output from a function an array from incoming datas like this example; example "Phone".
My code, modified from this example:

var m_out = [];
for (int i=0; i<=3; i++) {
var newmsg = {payload:msg.payload.abc[i].date, topic:"test"}
m_out.push(newmsg);
}
return [m_out];

How can I create the output as array and how can I access to the array? I dont' see in the debug an array but only the different output messages :-/
What I do wrong?
Thanks a lot!

2

Not sure exactly what you mean. Do you mean you want to pass on a message with an array of values in msg.payload for access by later nodes?

3

Thank you for the fast answer @Colin
Sorry for by bad english.
Oh sorry. I try to explain it more detailed:
I get datas from a http request (format json) and can access with this command: msg.payload.abc[i].date
Now, I have to convert the datas in a oder data/time format (i have just the function) and so I want to put out the modifed datas in an array format where I can access on the single data array like msg.payload.xyz[i].

4

If you "just" need to play with elements in an array then the javascript .map function is probably your best bet.

5

In your function, instead of creating an array of messages create an array of values, so something like

m_out.push(msg.payload.abc[i].date)

then at the end

msg.payload = m_out
return msg

Then in the next node you can reference msg.payload[i]

As @dceejay suggests you could use the javascript map function instead of a loop in the function.

6

@Colin
Thanks a lot for your inputs and the code example. It works!!!

@colin @dceejay
Thanks for your inputs.
I will search info about the javascript map function.

Thanks!!!

7

Now I try to use the javascript map function.
I'm a beginner with javascript a so I have some problems...
How the function know, which function the must run for begin and which function is a subfunction.
My code, where I hope that it works:

function outputdatetime ()   {
    const array1= [];
    
    for (i = 0; i <=3; i++) {
        array1[i] = msg.payload.dayForecasts[i].date;
        const map1 = array1.map(convertdatetime);
        }
msg.payload = map1;        
return msg;
}


function convertdatetime (datetime)   {
    var d = new Date(datetime);
    var year = d.getFullYear();
    var month = d.getMonth()+1;
    var day = d.getDate();
    
    if(day.toString().length==1){
        day = '0' + day;
    }
    
    if(month.toString().length==1){
        month = '0' + month;
    }
    
   return (day + '.' + month + '.' + year);
}

Thanks for your support!

8

You don't need the loop when you use the map function, it transforms the whole array. Look at the examples at the end of this

9

Perfect, thank you for your answer! :wink:
A general question:
In javascript how a function know, which function must run for begin and which function is a subfunction? For example i know in C/C++ it is void main().
Someone know where can I find on the web good infos for learning javascript?
Thanks!

10

Assuming you are talking about js in a Function node then there is no equivalent of main(). The code in the node will do nothing until it receives a message, at which time execution starts at the beginning of the Function node code. Obviously any functions defined there are skipped over to find the entry point.

11

@Colin
Thanks for your detailed answer!