Static changed 

pub static changed: ChangedInternalType

The .changed() function is called when the value of an element changes. This can be used to attach an element specific event listener.

Examples

let sel;

function setup() {
  textAlign(CENTER);
  background(200);
  sel = createSelect();
  sel.position(10, 10);
  sel.option('pear');
  sel.option('kiwi');
  sel.option('grape');
  sel.changed(mySelectEvent);
}

function mySelectEvent() {
  let item = sel.value();
  background(200);
  text("it's a " + item + '!', 50, 50);
}

let checkbox;
let cnv;

function setup() {
  checkbox = createCheckbox(' fill');
  checkbox.changed(changeFill);
  cnv = createCanvas(100, 100);
  cnv.position(0, 30);
  noFill();
}

function draw() {
  background(200);
  ellipse(50, 50, 50, 50);
}

function changeFill() {
  if (checkbox.checked()) {
    fill(0);
  } else {
    noFill();
  }
}

Parameters

fxn function to be fired when the value of an element changes. if false is passed instead, the previously firing function will no longer fire.