I am receiving undefined when using charAt[i]

[espruino-discuss]

Posted at 2014-12-01 by d0773d

I am not sure why I am receiving undefined when I loop through data which is a string, To see if data contained a string I did console.log(typeof data + ": " + data); which echoed out String : 26.19. From my understanding, I thought looping through the data string and using charAt[i] I should in theory return the character at i, however, I am receiving undefined. Why is that and how do I return the character at i?

s7s.prototype.sendValue = function (data) {
  var a = this.address;
  var length = data.length;
  var i;
  var val;
  var dpLoc;

  console.log(typeof data + ": " + data); //echos out a string

  for(i=0; i<data.length; i++) {
    var char = data.charAt[i];

    console.log(data.charAt[i]);

    if(char != ".") {
      val += char;
    }

    if(char == ".") {
      dpLoc = i;
    }
  }

  //console.log(val);

  //I2C2.writeTo(a, value);
};

[espruino-discuss]

Posted at 2014-12-02 by d0773d

Using var char = data.substr(i, 1); seems to work.

[espruino-discuss]

Posted at 2014-12-02 by Manxome

Finally found it! Try data.charAt(i) instead of data.charAt[i], or simply data[i] :)

[espruino-discuss]

Posted at 2014-12-02 by d0773d

doh! I used brackets instead of parentheses. data.charAt(i); works.

Code:

s7s.prototype.sendValue = function (data) {
  var a = this.address;
  var clr = this.displayTable.Clear; //Display clear command
  var dpc = this.displayTable.dp.cmd; //Decimal point command
  var dplo = this.displayTable.dp.location; //Decimal point location map

  var i;
  var length = data.length;
  var dpLoc;
  var value = "";

  for(i=0; i<length; i++) {
    var char = data.charAt(i);

    if(char != ".") {
      value += char;
    }

    if(char == ".") {
      dpLoc = i;
    }
  }

  I2C1.writeTo(a, clr); //Clear display
  I2C1.writeTo(a, value);

  if(typeof dpLoc !== 'undefined') {
    I2C1.writeTo(a, dpc);
    I2C1.writeTo(a, dplo[dpLoc - 1]);
  }
};

[espruino-discuss]

Posted at 2014-12-02 by Manxome

Two thoughts:

if (char != ".") { value += char; }
else { dpLoc = i; }

'data' always has a decimal point?

I2C1.writeTo(a, dpc);
  if(typeof dpLoc !== 'undefined') {
    I2C1.writeTo(a, dplo[dpLoc - 1]);
  }

[espruino-discuss]

Posted at 2014-12-02 by d0773d

No, results don't always have to return in a decimal format, however, in this case they will. I have
if(typeof dpLoc !== 'undefined')
For the moments where I wont, for example, taking a PPM reading of a solution. That was my attempt to write a generic function to output a result to my 4 - digit 7 segment display.

[espruino-discuss]

Posted at 2014-12-02 by Manxome

Doh, I get it now, wasn't reading carefully enough and missed the two I2CI.writeTo()'s before the decimal point check, sorry, my bad!

[espruino-discuss]

Posted at 2014-12-02 by d0773d

If data is 1234 and there is no decimal point in the value, the display will only show 1234. I still have to add checks for how many digits and if the display comma needs to be enabled or not. For example, 25.2'C. I have an idea:
code:

if (char == "'") { 
I2C1.writeTo (a,0b00001000);  //turn on comma}

[espruino-discuss]

Posted at 2014-12-02 by Manxome

yeah, sorry, I just realized that and edited my comment, sorry :)