how to implement a simple typesafe assertion library in Typescript?

we can assert typesafe to ensure that parameters with specific type in typescript.

here i will demostrate a simple function to ensure that input parameters are the same type

type is={

    <T>(a: T, b:T):boolean

}

let isSame:is=<T>(

    first:T,

    second:T

)=>{

    return first==second;

}

function print(b:boolean){

    console.log(b);

}

print(isSame("string","anotherString"));

print(isSame(true,false));

print(isSame(42, 42));

print(isSame(10, 'foo'));

src/index.ts:73:18 - error TS2345: Argument of type '"foo"' is not assignable to parameter of type 'number'.

73 print(isSame(10, 'foo'));
                    ~~~~~


Found 1 error.



we can easily get the catch the error in compile time. that is the magic of typesafe in typescript, the compiler enforce the type-safe check in the compile time.