Reflect.set(obj, key, val)
is similar to the operator form
obj[key] = val
The difference are:
Reflect.setis a function. The function form is useful in functional programing or generating code at run time.
Reflect.setalso return true/false depends on success. The assignment form has no proper way to know if the operation is succesful.
Reflect.setprovides a this Binding for Getter/Setter Properties.