javascript - Understanding the window.event property and its usage

Question

I don't understand the motivation behind window.event or window.event.srcElement. In what context should one use this? What exactly does it represent in the DOM?

Answer 1

Here what w3school says about event object:

Events are actions that can be detected by JavaScript, and the event object gives information about the event that has occurred.

Sometimes we want to execute a JavaScript when an event occurs, such as when a user clicks a button.

You can handle events using:

node.onclick = function(e) {
  // here you can handle event. e is an object.
  // It has some usefull properties like target. e.target refers to node
}

However Internet Explorer doesn't pass event to handler. Instead you can use window.event object which is being updated immediately after the event was fired. So the crossbrowser way to handle events:

node.onclick = function(e) {
  e = e || window.event;
  // also there is no e.target property in IE.
  // instead IE uses window.event.srcElement
  var target = e.target || e.srcElement;
  // Now target refers to node. And you can, for example, modify node:
  target.style.backgroundColor = '#f00';
}