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Events

Events

Events are things that happen in the system you are programming, which the system tells you about so your code can react to them.

Events are fired to notify code of "interesting changes" that may affect code execution.

const btn = document.querySelector("button");

function random(number) {
  return Math.floor(Math.random() * (number + 1));
}

function setNewRgbColor() {
  const rndCol = `rgb(${random(255)} ${random(255)} ${random(255)})`;
  document.body.style.backgroundColor = rndCol;
}

// adding listener
btn.addEventListener("click", setNewRgbColor);

// removing listener
btn.removeEventListener("click", setNewRgbColor);

Mutliple handlers

myElement.addEventListener("click", functionA);
myElement.addEventListener("click", functionB);

EventTarget

EventTarget interface is implemented by objects that can receive events and may have listeners for them.

Any target of events implement three methods associated with this interface:

  • addEventListener()
  • removeEventListener()
  • dispatchEvent()

addEventListener()

Sets up a function that will be called when a specified event is delivered to the target.

targets

Common targets are:

  • Element (or its children)
  • Document and Window
  • other objects that support events

Event Types

Mouse Events

  • e.g. click, dblclick, mousedown, mouseup, mouseover, mousemove

Keyboard Events

  • e.g. keydown, keyup, keypress

Form Events

  • e.g. submit, change, focus, blur, input

Touch Events

  • e.g. touchstart, touchmove, touchend

Window Events

  • e.g. load, resize, scroll, unload

Clipboard Events

  • e.g. copy, cut, paste

Drag & Drop Events

  • e.g. drag, dragstart, dragend, drop
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