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

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

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

property value 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"
    />

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

And here is an example of how the error occurs in the index.ts file.

src/index.ts

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// 👇️ const input: HTMLElement | null
const input = document.getElementById('first_name');

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

The reason we got the error is that the return type of the document.getElementById method is HTMLElement | null and the value property doesn't exist in the HTMLElement type.

To solve the error, use a type assertion to type the element as an HTMLInputElement (or HTMLTextAreaElement if you're typing a textarea element).

src/index.ts

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

if (input != null) {
  const value = input.value;
  console.log(value); // 👉️ "Initial value"
}

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.

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('first_name') 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); // 👉️ "Initial 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.

You might also use the optional chaining (?.) operator to short-circuit if the reference is equal to null or undefined

src/index.ts

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

// 👇️ using optional chaining (?.)
const value = input?.value;

console.log(value); // 👉️ Initial value

The optional chaining operator short-circuits returning undefined if the reference is equal to null or undefined.

In other words, if the input variable stores a null value, we won't attempt to access the value property on null and get a runtime error.

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

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

Conclusion #

Borislav Hadzhiev