Function throw_error

where is this function useful?

suppose you want to ensure that the value returned by a function my_fn: <T>() => (T | undefined) is non-nullable. and if it is undefined, then the your current function scope to throw an error, so that it exits.

typically, you would have to do something like:

// example 1:
const my_var = my_fn()
if(my_var === undefined || my_var === null) {
	throw Error("`my_var` was not supposed to be undefined")
}

// example 2:
const my_path = normalizePath("path/to/file.ts")
if(!my_path.startsWith("./")) {
	throw Error(`expected a relative path, instead found: ${my_path}`)
}
Copy

but with this function, you can write more concise inline statements for invoking errors conditionally:

// example 1:
const my_var = (my_fn() ?? throw_error("`my_var` was not supposed to be undefined"))!

// example 2:
const
	temp = normalizePath("path/to/file.ts"),
	my_path = (temp.startsWith("./") ? temp : throw_error("expected a relative path, found:", temp))!
Copy