In Typescript, you can extend an interface with the Node type to specifically

Question

In Typescript, you can extend an interface with the Node type to specifically

I'm currently utilizing Cypress 10.
I came across the following code snippet:

 Cypress.Commands.add(
  'byTestId',
  // Taking the signature from cy.get
  <E extends Node = HTMLElement>(
    id: string,
    options?: Partial<
      Cypress.Loggable & Cypress.Timeoutable & Cypress.Withinable & Cypress.Shadow
    >,
  ): Cypress.Chainable<JQuery<E>> =
    cy.get(`[data-testid="${id}"]`, options),
);

Can you explain what E extends Node = HTMLElement means precisely? And is it possible to use E extends HTMLElement instead?
Is there any distinction between these two?

typescript cypress

Answer 1

Answer №1

E extends Node = HTMLElement is a generic type parameter with a constraint of Node, and if the TypeScript compiler cannot infer it, it will default to HTMLElement.

To understand the difference between Node and HTMLElement, you can refer to this question:

A node serves as the general term for any object in the DOM hierarchy. It could be a built-in DOM element like document or document.body, an HTML tag from the HTML code such as <input> or <p>, or even a text node created by the system to hold text within another element. Essentially, a node encompasses all DOM objects.

An element specifically denotes one type of node among different types present (text nodes, comment nodes, document nodes, etc.).

Answer 2

E extends Node = HTMLElement is a generic type parameter with a constraint of Node, and if the TypeScript compiler cannot infer it, it will default to HTMLElement.

To understand the difference between Node and HTMLElement, you can refer to this question:

A node serves as the general term for any object in the DOM hierarchy. It could be a built-in DOM element like document or document.body, an HTML tag from the HTML code such as <input> or <p>, or even a text node created by the system to hold text within another element. Essentially, a node encompasses all DOM objects.

An element specifically denotes one type of node among different types present (text nodes, comment nodes, document nodes, etc.).

In Typescript, you can extend an interface with the Node type to specifically

Answer №1

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