Consider this scenario where we have a function:
function myFunc(name: string, age: number){ }
If we want to convert the parameters of a function type into a tuple, we can achieve this by:
type TArgs = Parameters<typeof myFunc> // = [name: string, age: number]
Next, we aim to transform this tuple into an object type like the one shown below:
type TObj = {
name: string,
age: number
}
Is there a way for us to accomplish this?
After reading through the insightful comments from the Typescript Whisperers, it is clear that attempting to reverse engineer key-value pairs from the labeled tuple utility in TypeScript is not possible. Despite the initial temptation caused by the output like [name: string, age: number], it turns out that this structure is simply a labeled version of the tuple [string, number].
It is important to note that these labels serve a documentation and tooling purpose, rather than influencing variable naming during destructuring.
To illustrate this point further, here are some practical demonstrations:
"Labels don’t require us to name our variables differently when destructuring. They’re purely there for documentation and tooling."
For example, in the given code snippet on the (Playground), you can see how the types are enforced:
const iAmTArgs: TArgs = ["myString", 0] // This is valid as the type really is [string, number]
const iAmNotTArgs: TArgs = [0, 0] // This will throw an error as expected because 'number' is not assignable to 'string'
type NameArg = Parameters<typeof myFunc>[0] // This returns 'string'
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