How to get or access the properties and methods of header HTML element tags without errors in TypeScript?
Tags: typescript
Published: 2021-10-04 00:00:00

---
  title: How to get or access the properties and methods of header HTML element tags without errors in TypeScript?
  published: true
  tags: TypeScript
  date: Mon Oct 04 2021 05:30:00 GMT+0530 (India Standard Time)
  canonical_url: https://melvingeorge.me/blog/get-or-access-properties-methods-header-html-element-tag-without-errors-typescript
  cover_image: https://melvingeorge.me/_next/static/images/main-0a7f9dc6690884fb0cabe86a3d4a703a.jpg
  ---
  [Originally posted here!](https://melvingeorge.me/blog/get-or-access-properties-methods-header-html-element-tag-without-errors-typescript)
  
To get or access the properties and methods of the `header` HTML element tags without having errors or red squiggly lines in TypeScript, you have to assert the type for the `header` HTML element tag using the `HTMLElement` interface in TypeScript.

The errors or warnings are shown by the TypeScript compiler since the compiler doesn't know more information on the `header` HTML element tag ahead of time. But we know that we are referencing the `header` HTML tag and thus we can tell the compiler to use the `HTMLElement` interface which contains the declarations for properties and methods.

### TL;DR

```ts
// get reference to the first 'header'
// HTML element tag in the document
// with type assertion using the HTMLElement interface
const headerTag = document.querySelector("header") as HTMLElement;

// no errors or red squiggly lines will be
// shown while accessing properties or methods
// since we have asserted the type
// for the 'header' HTML element tag 😍
const id = headerTag.id;
```

To understand it better let's say we are selecting the first `header` HTML element tag using the `document.querySelector()` method like this,

```ts
// get reference to the first 'header'
// HTML element tag in the document
const headerTag = document.querySelector("header");
```

Now let's try to get the value of a property called `id` which is used in the `header` HTML element tag as an attribute.

It can be done like this,

![error while accessing the id property in the header HTML element tag](https://melvingeorge.me/_next/static/images/headertag-id-error-2c8d77b7bad5b134c354dca09ddd652b.png)

As you can see that the TypeScript compiler is showing a red squiggly line below the `headerTag` object. If you hover over the `headerTag` you can see an error saying `Object is possibly 'null'`. This is because TypeScript is not sure whether the `headerTag` object will have properties and methods ahead of time.

Now to avoid this error we can assert the type for the `header` HTML element tag using the `HTMLElement` interface in TypeScript.

To do Type assertion we can use the `as` keyword after the `document.querySelector("header")` method followed by writing the interface name `HTMLElement`.

It can be done like this,

```ts
// get reference to the first 'header'
// HTML element tag in the document
// with type assertion using the HTMLElement interface
const headerTag = document.querySelector("header") as HTMLElement;

// no errors or red squiggly lines will be
// shown while accessing properties or methods
// since we have asserted the type
// for the 'header' HTML element tag 😍
const id = headerTag.id;
```

Now if hover over the `id` property in the `headerTag` object TypeScript shows more information about the property itself which is again cool and increases developer productivity and clarity while coding.

![more information about the id property in the header HTML element tag](https://melvingeorge.me/_next/static/images/more-info-id-property-header-tag-b65777b1125a7e43180f59860c580f70.png)

See the above code live in [codesandbox](https://codesandbox.io/s/get-or-access-properties-methods-header-html-element-tag-without-errors-typescript-iqexu?file=/src/index.ts).

That's all 😃!

### Feel free to share if you found this useful 😃.

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