[英]Replace/Override/Overwrite e.target in a JavaScript Event
There's a JS Fiddle here , can you replace e.target without cloning to a new object? 这里有一个JS小提琴 ,你可以在不克隆到新对象的情况下替换e.target吗?
The listeners from that fiddle are repeated below; 来自那个小提琴的听众在下面重复;
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')
}));
});
I've updated your fiddle ( http://jsfiddle.net/8AQM9/33/ ), as you said, event.target is readonly, but we can overwrite the property descriptor with Object.create
. 我已经更新了你的小提琴( http://jsfiddle.net/8AQM9/33/ ),如你所说,event.target是readonly,但我们可以用
Object.create
覆盖属性描述符。
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. 你是在正确的方式,但
Object.create
不会只返回key: value
hashmap,它会重现key: property-descriptor
你可以在MDN看到属性描述符是怎样的。
I've replaced 我已经换了
Object.create(e, {
target: document.createElement('p')
});
With 同
Object.create(e, {
target: {
value: document.createElement('p')
}
});
And this will prototype e
and modify the target
property of the new object. 这将原型
e
并修改新对象的target
属性。
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