In this article, we are going to learn the different ways of asserting the type of an HTMLElement in TypeScript. The type assertion is used to type the simple variables to JavaScript objects by defining the HTML element name.

There are many ways of performing this task as listed below:

Typing using the colon syntax

This is the general way of typing the variables in TypeScript that can also be used to assert the HTMLElement as well in TypeScript.

Syntax:

const var_name: type = value;

Example: The below example will show you how the colons can be used to assert HTMLElement in TypeScript.

HTML

Output:

Object

Using <> to assert typecast

In this approach, we will assert the type by specifying it inside the angular brackets (<>) just before the document selection of the element.

Syntax:

const var_name = <HTMLType> document.getElementById(ID');

Example: The below example will explain how you can assert HTMLElement using the angular brackets syntax.

HTML

Output:

Object

Using item() method with asserting type

In this approach, we will select the typecasting element using the tagname and the item() method and then type it using as typingProperty.

Syntax:

const var_name = document.getElementsByTagName('tag_name').item(0) as assertionType

Example: The below example will show the use of the item() method to assert type.

HTML

Output:

Object

Using the any type with asserting type

This approach will use the <any> type after the specified asserting type and define booth of them before accessing the element from DOM.

Syntax:

const var_name = (<assertingType> <any> document.getElementsByTagName('tag_name'))[0];

Example: The below example will show how to assert type with the help of the any type.

HTML

Output:

Object