How to get or access the properties and methods of meta HTML element tags without errors in TypeScript?

Published September 27, 2021

To get or access the properties and methods of the meta HTML element tags without having errors or red squiggly lines in TypeScript, you have to assert the type for the meta HTML element tag using the HTMLMetaElement interface in TypeScript.

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

TL;DR

// get reference to the first 'meta'
// HTML element tag in the document
// with type assertion using the HTMLMetaElement interface
const metaTag = document.querySelector("meta") as HTMLMetaElement;

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

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

// get reference to the first 'meta'
// HTML element tag in the document
const metaTag = document.querySelector("meta");

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

It can be done like this,

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

Now to avoid this error we can assert the type for the meta HTML element tag using the HTMLMetaElement interface in TypeScript.

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

It can be done like this,

// get reference to the first 'meta'
// HTML element tag in the document
// with type assertion using the HTMLMetaElement interface
const metaTag = document.querySelector("meta") as HTMLMetaElement;

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

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

See the above code live in codesandbox.

That's all 😃!

Feel free to share if you found this useful 😃.


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