Why do I hate js

this.load = (getManagersOptionsM, callback) => {
                clearTimeout(getManagerUsers);
                getManagerUsers = setTimeout(() => {
                    var notNull = getManagersOptionsM.DepartmentCodes != null && getManagersOptionsM.ProjectCodes != null && getManagersOptionsM.ClauseCodes != null;
                    var hasValues = getManagersOptionsM.DepartmentCodes.length > 0 && getManagersOptionsM.ProjectCodes.length > 0 && getManagersOptionsM.ClauseCodes.length > 0;
                    var valueNotNull = hasValues && getManagersOptionsM.DepartmentCodes[0] !== "" && getManagersOptionsM.ProjectCodes[0] !== "" && getManagersOptionsM.ClauseCodes[0] !== "";
                    if (notNull && valueNotNull) {
                        getManagersOptionsM.InvoiceId = this.invoiceId;
                        Api.AsyncClient.current.getManagersUsers(getManagersOptionsM, (result) => {
                            var canAgreeInvoice = result.filter((u) => { return u.CanAgreeInvoice });
                            var canApproveInvoice = result.filter((u) => { return u.CanApproveInvoice });
                            var otherUsers = result.filter((u) => { return !u.CanAgreeInvoice && !u.CanApproveInvoice });
                            var values = [];
                            var emptyAgreeAndApprove = canAgreeInvoice.length === 0 && canApproveInvoice.length === 0;

                            if (this.userRole === Api.Roles.Inspector) {
                                values = canApproveInvoice.concat(canAgreeInvoice).concat(otherUsers);
                            } else {
                                values = canAgreeInvoice.concat(canApproveInvoice).concat(otherUsers);
                            }
                            callback(values, emptyAgreeAndApprove);
                        });
                    }
                }, 300);
            }