Reflect.getMetadata return undefined only in IE11

[vincedan]

I am learning Decorators and found issue running in IE11, but no problem in chrome and Edge....

only in IE11, Relect.getMetadata() will return undefined.... but in Chrome and edge.. there is no problem.. I only post related part here

function validate<T>(target: any, propertyKey: string, descriptor: TypedPropertyDescriptor<T>) {
    let set = descriptor.set;
    descriptor.set = function (value: T) {
        let type = Reflect.getMetadata("design:type", target, propertyKey);   // return undefined.