CompositeAPI: Referencing HTML Object Template - Error TS2339 and TS2533 when using .value to access Proxy Object

Question

CompositeAPI: Referencing HTML Object Template - Error TS2339 and TS2533 when using .value to access Proxy Object

Having trouble referencing an element in VueJS 3 CompositeAPI. In my current implementation, it looks like this:

<div ref="myIdentifier"></div>

setup() {
  const myIdentifier = ref(null);
  onMounted(() => {
    console.log(myIdentifier.value); // When I try to access the value here, it returns a Proxy object instead of the Element object. Why is that happening?
    console.log(myIdentifier.value.$el); // This line successfully returns the Element object
    // The struggle continues:
    // TypeScript keeps complaining with error TS2339 'Property ... does not exist on type 'never"
    // even if I escape with myIdentifier.value?.$el or myIdentifier.value!.$el: TS2533 Object is possibly 'null' or 'undefined'

  });

  return {};
},

I feel like I might be missing something crucial here. My main aim is to easily have access to the HTML Element reference without having to deal with so much escaping and complexity.

Any help is greatly appreciated.

typescript vue.js

Answer 1

Answer №1

To start, in the context of TypeScript, it is important to clearly define what myIdentifier represents.

const myIdentifier = ref<HTMLDivElement>(); // Ref<HTMLDivElement | undefined>

Next, to retrieve the referenced HTML element, you can use the following syntax:

onMounted(() => {
      console.log(myIdentifier.value) // HTMLDivElement | undefined
      console.log(myIdentifier.value?.style) // CSSStyleDeclaration | undefined
});

It's crucial to include a question mark when accessing properties of myIdentifier.value, such as myIdentifier.value?.style, as it may be undefined. This is particularly relevant if you forget to add ref="myIdentifier" to your html element.

In your scenario, the issue arises because you fail to return the template ref myIdentifier from the setup() function.

setup() {
  const myIdentifier = ref<HTMLDivElement>();

  onMounted(() => { /* do sth with myIdentifier */ });

  return { 
    myIdentifier 
  };
},

This adjustment resolves the problem.

Edit: Additionally, addressing your other inquiry,

console.log(taskSliderCard.value); // returns a Proxy object. WHY???

While not entirely clear what taskSliderCard signifies, it likely points to a Vue component (

<TaskSliderCard ref="taskSliderCard" />

). Consequently, taskSliderCard.value yields the component instance rather than an HTML element.

Since it does not yield an HTML element, you must specify a different type for your taskSliderCard ref within the setup() method, like so:

import { TaskSliderCard } from 'your-ui-library'
...
setup() {
    // Determine the type of TaskSliderCard component
    // Ensuring TypeScript compiler recognizes its properties
    const taskSliderCard = ref<InstanceType<typeof TaskSliderCard>>();

    onMounted(() => {
      console.log(taskSliderCard.value?.$el) // HTMLElement | Undefined

    });

    return { taskSliderCard};
},

Answer 2

To start, in the context of TypeScript, it is important to clearly define what myIdentifier represents.

const myIdentifier = ref<HTMLDivElement>(); // Ref<HTMLDivElement | undefined>

Next, to retrieve the referenced HTML element, you can use the following syntax:

onMounted(() => {
      console.log(myIdentifier.value) // HTMLDivElement | undefined
      console.log(myIdentifier.value?.style) // CSSStyleDeclaration | undefined
});

It's crucial to include a question mark when accessing properties of myIdentifier.value, such as myIdentifier.value?.style, as it may be undefined. This is particularly relevant if you forget to add ref="myIdentifier" to your html element.

In your scenario, the issue arises because you fail to return the template ref myIdentifier from the setup() function.

setup() {
  const myIdentifier = ref<HTMLDivElement>();

  onMounted(() => { /* do sth with myIdentifier */ });

  return { 
    myIdentifier 
  };
},

This adjustment resolves the problem.

Edit: Additionally, addressing your other inquiry,

console.log(taskSliderCard.value); // returns a Proxy object. WHY???

While not entirely clear what taskSliderCard signifies, it likely points to a Vue component (

<TaskSliderCard ref="taskSliderCard" />

). Consequently, taskSliderCard.value yields the component instance rather than an HTML element.

Since it does not yield an HTML element, you must specify a different type for your taskSliderCard ref within the setup() method, like so:

import { TaskSliderCard } from 'your-ui-library'
...
setup() {
    // Determine the type of TaskSliderCard component
    // Ensuring TypeScript compiler recognizes its properties
    const taskSliderCard = ref<InstanceType<typeof TaskSliderCard>>();

    onMounted(() => {
      console.log(taskSliderCard.value?.$el) // HTMLElement | Undefined

    });

    return { taskSliderCard};
},

CompositeAPI: Referencing HTML Object Template - Error TS2339 and TS2533 when using .value to access Proxy Object

Answer №1

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