Seems like putting this manually through Babel: update(() => { this.order.propertyAddress = val.toLowerCase() if (!updateSelect(this.order.propertyAddress, this.order.propertyData != null ? this.order.propertyData.type : "")) { this.order.propertyData.data = null } }) Resulting in this: update(function () { _this.order.propertyAddress = val.toLowerCase(); if (!updateSelect(_this.order.propertyAddress, _this.order.propertyData != null ? _this.order.propertyData.type : "")) { _this.order.propertyData.data = null; } }) Made the trick…