javascript - lowdb 添加/编辑/更新/删除成功，但需要使用 if/then/else 语句对更新部分进行一些更改

Question

我已经使用express和lowdb数据库完成了添加/删除/编辑/更新代码，但它非常基本，尤其是在更新部分，而我想使用if/then/else语句，但我的小脑袋做不到独自一人；代码如下:

/* Update the data from displayed table of editup.pug */
router.post('/update', (req, res, next) =>  {
  db.read(); //read current datas in db
  let uid = req.body.id; // transfer "id" from TABLE to "uid"
/* Do actual updation of User via ID */
  db.get('users')
  .find({id: uid})
  .assign({First_Name: req.body.First_Name})
  .assign({Middle_Name: req.body.Middle_Name})
  .assign({Last_Name: req.body.Last_Name})
  .assign({Email: req.body.Email})
  .write();
/* Do actual updation of User via ID ends here */
 res.status(200);
res.redirect('/');
});

完整代码如下:

app.js

var port = 3000
var createError = require('http-errors');
var express = require('express');
var path = require('path');
var logger = require('morgan');

var indexRouter = require('./routes/index');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', indexRouter);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

app.listen(port, () => console.log(`Example app listening on port ${port}!`))

index.js

var express = require('express');
var router = express.Router();
var shortid = require('shortid');

var low = require('lowdb');
var FileSync = require('lowdb/adapters/FileSync');
var adapter = new FileSync('./DBase/shortIdDB.json');
var db = low(adapter);

// default user list
 db.defaults({ users: [] }).write();

/* GET data listing. Display list of current data in table */
router.get('/', (req, res, next) =>  {
 db.read(); //read current datas in db
 var putusers=db.get('users'); // use 'users:' section of db
 var data = putusers.value(); // transfer values from getusers to data
 res.render('index', { data }); // Send values from data to Table
console.log('Your Datas:', data);
});

// Form post -- Start adding data from FORM to DB
router.post('/add', (req, res) => {
 db.read(); //read current datas in db
 /* start collecting data from FORM */
 var FormFeed = {
	id:  shortid.generate(),
	First_Name: req.body.FName, 
	Middle_Name: req.body.MName, 
	Last_Name: req.body.LName, 
	Email: req.body.EMail}; 
/* collect data from FORM end here */	
 db.get('users').push(FormFeed).write(); // push and write to the db
res.redirect('/');
});

// delete selected record via id
router.get('/delete', function(req, res) {
 db.read(); //read current datas in db
 let uid = req.query.id;  // transfer "id" from TABLE to "uid"
 let data = db.get('users').find({ id: uid }).value(); // find and collect data via "uid"
 console.log("User to Process: ", data, "and the id: ", uid);
 /* Do actual deletion of User via ID */
	db.get('users')
	.remove({ id: uid })
	.write();
 /* Do actual deletion of User via ID End here!!! */
 res.status(200);
res.redirect('/');
 });

/* GET data via ID to update and display data in table */
router.get('/toupdate', (req, res, next) =>  {
  db.read(); //read current datas in db
  let uid = req.query.id; // transfer "id" from TABLE to "uid"
  let dataup = db.get('users').find({ id: uid }).value(); // find and collect data via "uid"
  console.log("User to Process: ", dataup, "and the id: ", uid);
res.render('editup', { dataup }); // Send values from data to Table
});

/* Update the data from displayed table of editup.pug */
router.post('/update', (req, res, next) =>  {
  db.read(); //read current datas in db
  let uid = req.body.id; // transfer "id" from TABLE to "uid"
/* Do actual updation of User via ID */
  db.get('users')
  .find({id: uid})
  .assign({First_Name: req.body.First_Name})
  .assign({Middle_Name: req.body.Middle_Name})
  .assign({Last_Name: req.body.Last_Name})
  .assign({Email: req.body.Email})
  .write();
/* Do actual updation of User via ID ends here */
 res.status(200);
res.redirect('/');
});

module.exports = router;

index.pug

extends layout
block content
  .container
    h2 NodeJs Express LowDB - View Add, Edit/Update, Delete records
    .success
    .error
    form(id='form1' method='post')
      input#id(type='hidden', name='id', value='')
      table
        tr
          td(style='text-align: center')
            input#First_Name(type='text',name='FName', placeholder='First Name', value='')
            |      
            input#Middle_Name(type='text',name='MName', placeholder='Middle Name', value='')
            |      
            input#Last_Name(type='text',name='LName', placeholder='Last Name', value='')
            |      
            input#Email(type='text',name='EMail', placeholder='Email Address', value='')
            |      
            input#subbtn(type="submit" onclick="javascript: form.action='/Add'" Value='Add')

      tbody
      table
          tr
            th id
            th First Name
            th Middle Name
            th Last Name
            th Email
            th(colspan='2') Action 
          each users in data
            tr
              td= users.id 
              td= users.First_Name
              td= users.Middle_Name
              td= users.Last_Name
              td= users.Email
              td(id="tdclck1"): a(href='http://localhost:3000/toupdate?id='+users.id) Edit  
              td(id="tdclck2"): a(href='http://localhost:3000/delete?id='+users.id) Delete

editup.pug

extends layout
block content
  .container
    h2 NodeJs Express LowDB - View Add, Edit/Update, Delete records
    .success
    .error
    form(id='form2' method='post')
      table
          tr
            th id
            th First Name
            th Middle Name
            th Last Name
            th Email
            th Action
          tr()
            td()
             input(type='text',name='id',readonly,value=dataup.id)
            td()
             input(type='text',name='First_Name',value=dataup.First_Name)
            td()
             input(type='text',name='Middle_Name',value=dataup.Middle_Name)
            td()
             input(type='text',name='Last_Name',value=dataup.Last_Name)
            td()
             input(type='text',name='Email',value=dataup.Email)
            td
             input#subbtn(type="submit" onclick="javascript: form.action='/Update'" Value='Update')
    a(href="/") << back

shotidDB.json

{
  "users": [
    {
      "id": "-34BAqsS",
      "First_Name": "Kauna-unahan",
      "Middle_Name": "Kagitna-ginaan",
      "Last_Name": "Kahuli-hulihan",
      "Email": "sdfg@sdfv.dfc"
    },
    {
      "id": "wtWsbepJ",
      "First_Name": "Pangalan",
      "Middle_Name": "GitnangPangalan",
      "Last_Name": "HulingPangalan",
      "Email": "kljjl123@ooo.com"
    },
    {
      "id": "zyBMsLtJ",
      "First_Name": "Kalatsa",
      "Middle_Name": "palitsako",
      "Last_Name": "ayooo",
      "Email": "walay.ayo@abc.com"
    },
    {
      "id": "vxqDSrPm",
      "First_Name": "newuser",
      "Middle_Name": "newmid",
      "Last_Name": "newlast",
      "Email": "newmail@mail.com"
    },
    {
      "id": "ybl4yvNS",
      "First_Name": "Kaunaunahan Ngalan",
      "Middle_Name": "Kagitnagitnaan Pangalan",
      "Last_Name": "Apelyido",
      "Email": "kakaape@email.ph"
    }
  ]
}

我已经设法更改了实现 if/else 语句的更新部分，代码如下:

/* Update the data from displayed table of editup.pug Revision 1 */
router.post('/update', (req, res, next) =>  {
	
	db.read(); //read current datas in db
	let uid = req.body.id; // transfer "id" from TABLE to "uid"
	/* Do actual updation of User via ID */
	let dataup = db.get('users').find({ id: uid }).value();
		if (dataup.First_Name === req.body.First_Name) {
			console.log("No change in First_Name");
			} else {
				db.get('users').find({id: uid})
				.assign({First_Name: req.body.First_Name})
				.write();
				}
		if (dataup.Middle_Name === req.body.Middle_Name) {
			console.log("No change in Middle_Name");
			} else {
				db.get('users').find({id: uid})
				.assign({Middle_Name: req.body.Middle_Name})
				.write();
				}
		if (dataup.Last_Name === req.body.Last_Name) {
			console.log("No change in Last_Name");
			} else {
				db.get('users').find({id: uid})
				.assign({Last_Name: req.body.Last_Name})
				.write();
				}
		if (dataup.Email === req.body.Email) {
			console.log("No change in Email");
			} else {
				db.get('users').find({id: uid})
				.assign({Email: req.body.Email})
				.write();
				}
	/* Do actual updation of User via ID ends here */
res.status(200);
res.redirect('/');
});

Answer 1

好吧，我的建议是添加一个函数来为您执行此操作，因为有很多重复。

if (dataup.Last_Name === req.body.Last_Name) {
    console.log("No change in Last_Name");
} else {
    db.get('users').find({id: uid})
        .assign({Last_Name: req.body.Last_Name})
        .write();
}

像这样:

function updateUser(userParam, userId, dbIntance, dataup){

    if (dataup.userParam=== req.body.userParam) {
        console.log(`No change in ${userParam}`);
    } else {
        dbIntance.get('users').find({id: userId})
            .assign({userParam: req.body.userParam})
            .write();
    }
}

所以现在只需用这段代码替换所有的 if 即可。

const userDetail = ['First_Name ', 'Middle_Name', 'Last_Name', 'Email']

for(let i=0; i<userDetail.length; i++){
    this.updateUser(userDetail[i], uid, db, dataup);
}

干净、简洁是我们的目标，而且也不仅仅是基本的。您可以查看下面的链接，了解 Nodejs 的基于 Controller 的结构，这是一些帮助您继续前进的高级内容。希望它有帮助:)

https://developer.mozilla.org/en-US/docs/Learn/Server-side/Express_Nodejs/routes