There's a JS Fiddle here, can you replace e.target without cloning to a new object?

The listeners from that fiddle are repeated below;

one.addEventListener('click', function(e) {
  // default behaviour, don't modify the event at all
  logTarget(e);
});

two.addEventListener('click', function(e) {
  // replace the value on the same object, which seems to be read-only
  e.target = document.createElement('p');
  logTarget(e);
});

three.addEventListener('click', function(e) {
  function F(target) { 
    // set another property of the same name on an instance object
    // which sits in front of our event
    this.target = target;
  }
  // put the original object behind it on the prototype
  F.prototype = e;
  logTarget(new F(document.createElement('p')));
});

four.addEventListener('click', function(e) {
  // create a new object with the event behind it on the prototype and
  // our new value on the instance
  logTarget(Object.create(e, {
    target: document.createElement('p')
  }));
});

There's a JS Fiddle here, can you replace e.target without cloning to a new object?

The listeners from that fiddle are repeated below;

one.addEventListener('click', function(e) {
  // default behaviour, don't modify the event at all
  logTarget(e);
});

two.addEventListener('click', function(e) {
  // replace the value on the same object, which seems to be read-only
  e.target = document.createElement('p');
  logTarget(e);
});

three.addEventListener('click', function(e) {
  function F(target) { 
    // set another property of the same name on an instance object
    // which sits in front of our event
    this.target = target;
  }
  // put the original object behind it on the prototype
  F.prototype = e;
  logTarget(new F(document.createElement('p')));
});

four.addEventListener('click', function(e) {
  // create a new object with the event behind it on the prototype and
  // our new value on the instance
  logTarget(Object.create(e, {
    target: document.createElement('p')
  }));
});

• javascript
• object
• mouseevent
• prototype

1 Answer 1

I've updated your fiddle (http://jsfiddle/8AQM9/33/), as you said, event.target is readonly, but we can overwrite the property descriptor with Object.create.

You were on the right way but Object.create does not recive only the key: value hashmap, it recives key: property-descriptor you can see at MDN how a property descriptor is.

I've replaced

Object.create(e, {
    target: document.createElement('p')
});

With

Object.create(e, {
    target: {
        value: document.createElement('p')
    }
});

And this will prototype e and modify the target property of the new object.