> vanilla JavaScript that validates function arguments properly
Validating perfectly at run time is exceedingly difficult and tedious. Does anyone actually write defensive code like this?:
function sum(arr) {
if (!Array.isArray(arr))
throw "Invalid type";
let result = 0;
for (const val of arr) {
if (typeof val != "number")
throw "Invalid type";
result += val;
}
return result;
}
By contrast, the TypeScript code is reasonable:
function sum(arr: Array<number>) {
let result: number = 0;
for (const val of arr)
result += val;
return result;
}
> it does make the code more terse
No, TypeScript code with explicit type annotations is less terse than the typical unsafe JavaScript code that lacks type checks.
> It requires that you define types for every little thing
No, the TypeScript compiler has type inference. It can assign types based on how values are passed between known functions. While it's a good idea to explicitly type all function signatures in TypeScript, it's not mandatory unlike Rust.
Validating perfectly at run time is exceedingly difficult and tedious. Does anyone actually write defensive code like this?:
By contrast, the TypeScript code is reasonable: > it does make the code more terseNo, TypeScript code with explicit type annotations is less terse than the typical unsafe JavaScript code that lacks type checks.
> It requires that you define types for every little thing
No, the TypeScript compiler has type inference. It can assign types based on how values are passed between known functions. While it's a good idea to explicitly type all function signatures in TypeScript, it's not mandatory unlike Rust.