trim last character from string?

[espruino-discuss]

Posted at 2014-03-08 by d0773d

I read through the reference section of this website and could not find a trim or some sort of replace function. The issue I am having is, my PH sensor responds with a float(ie 8.55) with a length of 5. I think the fifth character is a carriage return. I could not tell so I used String.charCodeAt(5) which responded back with a 13. How do I remove the \r or any none digit character from the end of the float value? Since the value is sent via serial communication I tried:

If (e.data != "\r" || e.data != "\n") {
  phValue = e.data;
}

However, when I check the length of the phValue again I am still getting a length of 5.

[espruino-discuss]

Posted at 2014-03-09 by d0773d

I did:

phValue = phValue.substring(0, phValue.length - 1);

That code removes the last character as expected.

In my previous forum post I explained that I attempted to catch the \r by doing:

if (e.data != "\r" || e.data != "\n") {
      console.log("NO CR");
      phValue+=e.data;
    }

However, "NO CR" is echoing out 5 times instead of only 4. I have no idea why \r is getting stored to the phValue when the if statement I think should of filtered \r out. Can anyone explain why this is happening?

[espruino-discuss]

Posted at 2014-03-09 by d0773d

I started from scratch and removed the line:

phValue = phValue.substring(0, phValue.length - 1);

Everything seems to be working properly. I have no idea why, but starting from scratch seemed to do the trick.

[gfwilliams]

Posted at 2014-03-10 by @gfwilliams

I think your issue was e.data != "\r" || e.data != "\n" because it'll always be true - it should be e.data != "\r" && e.data != "\n"

I guess the thing to do is to use the \r as a signal that the data has ended:

if (e.data == "\r" || e.data == "\n") {
  print(myValue);
  myValue="";
} else {
  myValue+=e.data;
}

[espruino-discuss]

Posted at 2014-03-10 by d0773d

e.data != "\r" || e.data != "\n"

That was exactly the issue. I read the sensor module user guide again, it explained the results will end in a "\r". So I removed the checking for the newline character. As soon as I removed the newline check and only checked for a CR:

if (e.data != "\r")

It worked. When I get home from work I will implement your example.

[espruino-discuss]

Posted at 2014-03-26 by rwaldron

If the value is actually a floating point number, but you're receiving a string, then you should be able to simply coerce the value to a number and the non-numeric characters will be discarded:

var ph = "8.55\r\n";

+ph === 8.55; // true

Unfortunately, that doesn't seem to work correctly in Espruino. I've filed a bug: espruino/Espruino#268

[gfwilliams]

Posted at 2014-03-26 by @gfwilliams

Fixed now ;)

[espruino-discuss]

Posted at 2014-03-26 by rwaldron

claps