Get rid of the decimals in a json string.

[Marius Fosshagen Berget]

I feed the node-red with a json string who looks like this:

N/b827eb79e8ef/system/0/Dc/Battery/Current : msg.payload : Object{ "value": 0.8999999761581421 }
I want to forward this to freeboard, but only with 2 decimals.. So the number will be in this case 0.89 or 0.90 (dosent matter if it rounds the number or just remove the decimals)..Have searched the internet and found alot of complex ways who I dont understand mutch of :)
Anyone who have a quick and easy solution?

[Mark Setrem]

try

msg.payload= msg.payload.value.toFixed(2);
return msg;

in a function node

[steve rickus]

Hi Marius,

The debug output shows your msg is an object, not a string -- and yes, there are many ways to do what you want, but it depends on what you want to pass to Freeboard. Since I'm not familiar with it, I'll just assume you only need the numeric value of the object, rounded to 2 decimal places.

Simplest solution for a javascript programmer would be this 3 line function node (which returns a string):

var numval = msg.payload.value || -1;

msg.payload = numval.toFixed(2);

return msg;

[Marius Fosshagen Berget]

And the problem i solved! 

When I searched the internet yesterday I was close, but no cigar!

If I ever meet any of you I`ll buy you a beer, thnx for the effort.

[Colin Law]

On 15 March 2017 at 13:22, steve rickus <sri...@gmail.com> wrote:
> Hi Marius,
>
> The debug output shows your msg is an object, not a string -- and yes, there
> are many ways to do what you want, but it depends on what you want to pass
> to Freeboard. Since I'm not familiar with it, I'll just assume you only need
> the numeric value of the object, rounded to 2 decimal places.
>
> Simplest solution for a javascript programmer would be this 3 line function
> node (which returns a string):
>
> var numval = msg.payload.value || -1;

Won't that give a value of -1 if msg.payload.value is 0?

Colin

[steve rickus]

Why, yes, it would -- good catch! I tacked that on to be able to track missing values, but didn't test it.

I also didn't do any type checks/conversions for values that are NaN or strings, which would be good to add...

[Colin Law]

I usually user Number() in these circumstances and then check isNaN()
and isFinite() to check for a valid number

Colin

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[fluri...@gmail.com]

To get a float I usually do it this way: 

msg.payload.value = parseFloat((msg.payload.value ).toFixed(2));

 

[Colin Law]

I am not very familiar with freeboard, but does it not have display
formatting capability? If so then it is probably better to format it
at display time in freeboard rather than throwing away accuracy before
you need to.

Colin

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