The TrustedHTML interface of the Trusted Types API represents a string that a developer can insert into an injection sink that will render it as HTML. These objects are created via TrustedTypePolicy.createHTML() and therefore have no constructor.

The value of a TrustedHTML object is set when the object is created and cannot be changed by JavaScript as there is no setter exposed.

TrustedHTML.toJSON()

Returns a JSON representation of the stored data.

TrustedHTML.toString()

A string containing the sanitized HTML.

In the below example we create a policy that will create TrustedHTML objects using TrustedTypePolicyFactory.createPolicy(). We can then use TrustedTypePolicy.createHTML to create a sanitized HTML string to be inserted into the document.

The sanitized value can then be used with Element.innerHTML to ensure that no new HTML elements can be injected.

<div id="myDiv"></div>

const escapeHTMLPolicy = trustedTypes.createPolicy("myEscapePolicy", {
  createHTML: (string) => string.replace(/</g, "&lt;"),
});

let el = document.getElementById("myDiv");
const escaped = escapeHTMLPolicy.createHTML("<img src=x onerror=alert(1)>");
console.log(escaped instanceof TrustedHTML); // true
el.innerHTML = escaped;

• Prevent DOM-based cross-site scripting vulnerabilities with Trusted Types