TS 类型签名问题

Question

type IsType<T> = (val:any) => val is T;
let isObj: IsType<string>

isObj怎么赋值，才能不报错？谁能举个例子啊，研究了一下午，不知道该咋办！

Answer 1

type IsType<T> = (val:any) => val is T;
let isObj: IsType<string> = function (s): s is string { 
    return typeof s === 'string';
};