README - Type Challenges

<h1>IsFixedStringLiteralType </h1><blockquote><p>by 蛭子屋双六 <a href="https://github.com/sugoroku-y" target="_blank">@sugoroku-y</a></p></blockquote><p><a href="https://tsch.js.org/30970/play" target="_blank"></a>    <a href="./README.ja.md" target="_blank"></a> </p>

Sometimes you may want to determine whether a string literal is a definite type. For example, when you want to check whether the type specified as a class identifier is a fixed string literal type.

typescript

type Action<ID extends string> = { readonly id: ID };

Since it must be fixed, the following types must be determined as false.

never type
Union of string literal types
Template literal types with embedded string, number, bigint, boolean

Determine whether the given type S is a definite string literal type.