For pure educational and curiosity purposes, I am trying to create an element-wrapper object that allows me to tack-on my own properties and methods to an element. The behavior I'm trying to simulate is basically this:
// get a button element to wrap
const button = document.querySelector('button');
// some function that wraps new properties/methods around a given element
function wrap(element) {
this.customName = 'John';
this.customAge = 100;
this.printName = function() {
console.log(this.customName);
}
// ...
// ...somehow inherit element fields...
// ...
}
// wrap the button element
const customElement = new wrap(button);
// custom behavior:
console.log(customElement.customAge) // output => 100
customElement.printName() // output => 'John'
// legacy behavior
console.log(customElement.clientHeight) // output => client height
customElement.remove() // => should still call 'remove' on the element
So, here I should be able to add my own methods/properties but still access the original fields normally. Is this even possible?
I'm using a constructor function here as an example just to demonstrate the intended behavior, but I don't actually know if this would be relevant for the solution. I'm new to Javascript and I have done a ton of research on prototypes and classes, but I'm still confused on what approach I would take here.
Edit: As Brad pointed out in the comments, I also tried this implementation using classes:
class MyButton extends HTMLButtonElement {
constructor() {
super();
this.customName = 'John';
this.customAge = 100;
}
printName() {
console.log(this.customName);
}
}
const myBtn = new MyButton();
But this resulted in the error:
Uncaught TypeError: Illegal constructor
I haven't test this, but maybe something like this:
// get a button element to wrap
const button = document.querySelector('button');
// some function that wraps new properties/methods around a given element
function wrap(element) {
Object.defineProperties(element, {
customName: {value:"John"},
customAge: {value:100},
printName:{value: () => console.log(element.customName)}
})
return element
}
// wrap the button element
const customElement = wrap(button);
// custom behavior:
console.log(customElement.customAge) // output => 100
customElement.printName() // output => 'John'
// legacy behavior
console.log(customElement.clientHeight) // output => client height
customElement.remove() // => should still call 'remove' on the element<button>Hello world!</button>Another method could be used is wrap element into proxy()
This will allow return custom data if property doesn't exist and send notifications when properties changed:
const customElement = function (element, properties = {})
{
this.element = element;
this.customName = 'John';
this.customAge = 100;
this.printName = function() {
console.log(this.customName);
}
//override default properties
for(let i in properties)
{
if (i in element)
element[i] = properties[i];
else
this[i] = properties[i];
}
return new Proxy(this, {
get(target, prop)
{
if (prop in target.element) //is property exists in element?
{
if (target.element[prop] instanceof Function)
return target.element[prop].bind(target.element);
return target.element[prop];
}
else if (prop in target) //is property exists in our object?
return target[prop];
else
return "unknown property"; //unknown property
},
set(target, prop, value, thisProxy)
{
const oldValue = thisProxy[prop];
if (prop in target.element)
target.element[prop] = value;
else
target[prop] = value;
// send notification
target.element.dispatchEvent(new CustomEvent("propertyChanged", {
detail: {
prop,
oldValue,
value
}
}));
}
});
}
const button = new customElement(document.createElement("button"), {customName: "Not John"});
button.addEventListener("propertyChanged", e =>
{
console.log("property changed", e.detail);
});
button.printName();
console.log("age:", button.customAge);
console.log("height:", button.clientHeight);
console.log("blah:", button.blah);
button.blah = "ok";
console.log("blah:", button.blah);