Web Components & Shadow DOM

How do you handle form-associated custom elements?

class CustomInput extends HTMLElement {
  static formAssociated = true;
  
  constructor() {
    super();
    this._internals = this.attachInternals();
    this._value = '';
  }
  
  get value() { return this._value; }
  set value(v) {
    this._value = v;
    this._internals.setFormValue(v);
  }
}

By extending HTMLFormElement
Using the formAssociated static property
Form-associated custom elements are created by: 1) Setting static formAssociated = true in the element class, 2) Using attachInternals() to get an ElementInternals object, 3) Implementing proper value handling and form integration, 4) Setting form values using setFormValue(). This allows custom elements to participate in form submission and validation.
Through regular event handling
It's not possible to create form-associated elements

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