Based on the Type assertions part of the docs

Below we convert or cast from a string to a number.

This is useful when a value could have multiple types and you tell the compiler which one is in use here.

The as syntax

const foo = "this is a string";
const len = (foo as string).length;

Angle-bracket syntax

Same as above but not work with JSX syntax.

const foo = "this is a string";
const len = (<string> foo).length;