func (ctx ppctx) isBigNumber(v *otto.Object) bool { // Handle numbers with custom constructor. if v, _ := v.Get("constructor"); v.Object() != nil { if strings.HasPrefix(toString(v.Object()), "function BigNumber") { return true } } // Handle default constructor. BigNumber, _ := ctx.vm.Object("BigNumber.prototype") if BigNumber == nil { return false } bv, _ := BigNumber.Call("isPrototypeOf", v) b, _ := bv.ToBoolean() return b }