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javascriptnode.jsnode-red

How do you represent a number as a string in javascript?

I have a node-red flow that needs to create an MQTT payload.

The payload is a temperature reading from an I/O card, calculated as a float (73.4 for example).

I need the message payload to be a string, not a number; something like "Barn Temp is 73.2". How can I create this?

msg.payload = tempReading;               // gives a number
msg.payload = ""+tempReading;            // returns NaN

A bonus question: if I did use this as a numeric payload how can I specify its format? The reading is calculated at 73.18527461364; I need to send this as 73.2.

I'm having a devil of a time finding out how to format strings in javascript!

Solution

  • toString is an easy surefire way to convert numbers to strings.

    var x = 10.56;
x = x.toString();
console.log(x, typeof x);

    If you want to control how many decimal points are displayed, you can use toFixed.

    var x = 12.3456789;
x = x.toFixed(3);
console.log(x, typeof x);