Reflect.js
function GetMethod(V, P) {
            var func = V[P];
            if (func === undefined || func === null)
                return undefined;
            if (!IsCallable(func))
                throw new TypeError();
            return func;
        }
function GetMethod(V, P) {
            var func = V[P];
            if (func === undefined || func === null)
                return undefined;
            if (!IsCallable(func))
                throw new TypeError();
            return func;
        }
function GetMethod ( V , P ) { var func = V [ P ] ; if ( func === undefined || func === null ) return undefined ; if ( ! IsCallable ( func ) ) throw new TypeError ( ) ; return func ; }
7.3 Operations on Objects https://tc39.github.io/ecma262/#sec-operations-on-objects 7.3.9 GetMethod(V, P) https://tc39.github.io/ecma262/#sec-getmethod
7 . 3 Operations on Objects https : // tc39 . github . io / ecma262 / #sec - operations - on - objects 7 . 3 . 9 GetMethod ( V P ) https : // tc39 . github . io / ecma262 / #sec - getmethod