I can't think of a way to filters class properties by type as in the below code. And store it on a type not JavaScript just for the TypeScript part
class Test
{
func(){}
age:number = 5
name:string = '<my-name>'
}
type ClassPropetiesByType<ClassType,PropertiesTypes> = null // code will be here
type TestFunctions = getClassPropetiesByType<Test, Function> // => 'func'
type TestStrings = getClassPropetiesByType<Test, string> // => 'name'
type TestNumbers = getClassPropetiesByType<Test, number> // => 'age'