rbx-is-type
v0.0.2
Published
A simple library for two-step type-narrowing
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is-type
This library comes with two functions:
interface IsACheckableTypes extends CheckableTypes, Instances {}
/**
* Matches a given value to a given string type.
* @param type A string which will match to a typeof call, or will match an Object's ClassName
* @param value The value to match to a given type
*/
export declare function is<T extends keyof IsACheckableTypes>(type: T, value: any): value is IsACheckableTypes[T];
/**
* Matches a given value to a given string type.
* @param type A string which will match to a typeof call, or will match an Object:IsA(type) call
* @param value The value to match to a given type
*/
export declare function isA<T extends keyof IsACheckableTypes>(type: T, value: any): value is IsACheckableTypes[T];
The implementations are pretty obvious:
is = function(typeStr, obj)
local objType = typeof(obj);
return objType == typeStr or objType == "Instance" and obj.ClassName == typeStr;
end;
isA = function(typeStr, obj)
local objType = typeof(obj);
return objType == typeStr or objType == "Instance" and obj:IsA(typeStr);
end;
These are very useful for type narrowing:
function Get(data: unknown) {
if (is("number", data)) {
// data is a number
} else if (is("RemoteEvent", data)) {
// data is a RemoteEvent
} else if (isA("BasePart", data)) {
// data is a BasePart
}
}