Property 'X' does not exist on type 'HTMLElement' in TS

Property 'X' does not exist on type 'HTMLElement' in TS #

The error "Property 'X' does not exist on type 'HTMLElement'" occurs when we try to access a property that doesn't exist on an element of type HTMLElement. To solve the error, use a type assertion to type the element correctly before accessing the property.

property not exist type htmlelement

This is the index.html file for the examples in this article.

index.html

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<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
  </head>
  <body>
    <input
      id="first_name"
      type="text"
      name="first_name"
      value="Initial Value"
    />

    <a id="link" href="https://google.com" target="_blank">Open Google</a>

    <button id="btn">Submit</button>

    <script src="./src/index.ts"></script>
  </body>
</html>

And here are 3 examples of how the error occurs in the index.ts file.

src/index.ts

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const input = document.getElementById('input');

if (input != null) {
  // ⛔️ Property 'value' does not exist on type 'HTMLElement'.ts(2339)
  const value = input.value;
  console.log(value);
}

// ---------------------------

const link = document.getElementById('link');

if (link != null) {
  // ⛔️ Property 'href' does not exist on type 'HTMLElement'.ts(2339)
  const href = link.href;
  console.log(href);
}

// ---------------------------

const btn = document.getElementById('btn');

if (btn != null) {
  // ⛔️ Property 'disabled' does not exist on type 'HTMLElement'.ts(2339)
  btn.disabled = true;
}

The reason we got the error is that the return type of the document.getElementById method is HTMLElement | null and the properties we tried to access don't exist on the HTMLElement type.

To solve the error, use a type assertion to type the element correctly, e.g. as HTMLInputElement, HTMLButtonElement, HTMLAnchorElement, HTMLImageElement , HTMLTextAreaElement, etc - depending on the type of element you are working with.

The types are consistently named as HTML***Element. Once you start typing HTML.., your IDE should be able to help you with autocomplete.

src/index.ts

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const input = document.getElementById('input') as HTMLInputElement | null;

if (input != null) {
  const value = input.value;
  console.log(value);
}

// ---------------------------

const link = document.getElementById('link') as HTMLAnchorElement | null;

if (link != null) {
  const href = link.href;
  console.log(href);
}

// ---------------------------

const btn = document.getElementById('btn') as HTMLButtonElement | null;

if (btn != null) {
  btn.disabled = true;
}

Type assertions are used when we have information about the type of a value that TypeScript can't know about.

We effectively tell TypeScript that the input variable stores anHTMLInputElement or a null value and not to worry about it.

Similarly, we typed the link variable to be an HTMLAnchorElement or null and the btn variable - HTMLButtonElement or null.

We used a union type to specify that the variable could still be null, because if an HTML element with the provided id does not exist in the DOM, the getElementById() method returns a null value.

We used a simple if statement that serves as a type guard to make sure the input variable doesn't store a null value before accessing its value property.

src/index.ts

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const input = document.getElementById('input') as HTMLInputElement | null;

// 👉️ input has type HTMLInputElement or null here

if (input != null) {
  // 👉️ input has type HTMLInputElement here
  const value = input.value;
  console.log(value);
}

TypeScript knows that the input variable has a type of HTMLInputElement in the if block and allows us to directly access its value property.

It's always a best practice to include null in the type assertion because the getElementById method would return null if no element with the provided id was found.

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Property 'X' does not exist on type 'HTMLElement' in TS

Property 'X' does not exist on type 'HTMLElement' in TS #

Conclusion #

Borislav Hadzhiev