uniapp之uni.showModal 弹出多次导致重叠问题

 if (code && code == 401) {  
            let exists = uni.getStorageSync('token_expired') || false  
            if (!exists) {  
                uni.setStorageSync('token_expired', true)  
                uni.showModal({  
                    content: msg,  
                    showCancel: false,  
                    confirmText: "确认",  
                    success: (res) => {  
                        if (res.confirm) {  
                            store.dispatch('auth/logout')  
                            uni.reLaunch({  
                                url: '/pages/login/index'  
                            })  
                        }  
                    }  
                })  
            }  
        }