source used: https://github.com/p5-serial/p5.serialport

https://github.com/p5-serial/p5.serialcontrol/releases

void setup(){
  Serial.begin(9600);
}

void loop(){
  int potentiometer = analogRead(A0);
  int mappedPot = map(potentiometer,0,1023,0,255);
  Serial.println(mappedPot);
  delay(1);
}

shows:

void setup(){
  Serial.begin(9600);
}

void loop(){
  int potentiometer = analogRead(A0);
  int mappedPot = map(potentiometer,0,1023,0,255);
  Serial.write(mappedPot);
  delay(1);
}

shows:

in p5 Editor

p5.js Web Editor

• in Sketch.js
• in index.html
• in style.css
• in p5.serialport.js