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 because 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.

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

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

Borislav Hadzhiev