rohitranjan-2702 / commonErrorsDEV

Solutions to some common issue/errors that developers face. Send your errors below. I'll be glad to help you out.

commonErrorsDEV

Solutions to some common issue/errors that developers face.

- Download a databse from Mongodb Atlas {with connection url string}

Run this command in the command prompt mongoexport --uri mongodb+srv://<username>@atlas-cluster-url.mongodb.net/<db-name> --collection <collection-name> --out <path-to-export>

Install MongoDB Tools from here: https://www.mongodb.com/try/download/database-tools

- Error: Can't set headers after they are sent to the client

usually happens when you send several responses for one request. Make sure the following functions are called only once per request:

res.json() res.send() res.redirect() res.render()

Only one response can be sent per request! Remember!

1. Running 'vercel' command after installing vercel 'npm i -g vercel'

ERROR:

vercel : File C:\Users\user\AppData\Roaming\npm\vercel.ps1 cannot be loaded because running scripts is disabled on this system. For more information, see
about_Execution_Policies at https:/go.microsoft.com/fwlink/?LinkID=135170.

Solution

run the command like this

  Set-ExecutionPolicy RemoteSigned -Scope CurrentUser

Now you are good to go!

Why this happens?

2. CORS (Cross-Origin Resource Sharing) error, which comes when an application running on one port accesses application running on another port.

Solution

We will be serving both react and Nodejs apps on the same port add new scripts in package.json file.

"start-server": "node server/index.js",  
"start-app": "npm run build && npm run start-server"

So your package.json scripts section will look like this

Here in the start-app script, we are running npm run build script first and then npm run start-server

So from the terminal execute the following command.

npm run start-app

This will create build folder with all of our react code and start the express server of server/index.js file so now both react and Nodejs app is accessible on the same 3030 port.

If you navigate to http://localhost:3030/ , you will see that our application still works.

Include this in server.js :

const buildPath = path.join(__dirname, '..', 'build');
app.use(express.json());
app.use(express.static(buildPath));

var schema = new Schema({
  name:    String,
  binary:  Buffer,
  living:  Boolean,
  updated: { type: Date, default: Date.now },
  age:     { type: Number, min: 18, max: 65 },
  mixed:   Schema.Types.Mixed,
  _someId: Schema.Types.ObjectId,
  decimal: Schema.Types.Decimal128,
  array: [],
  ofString: [String],
  ofNumber: [Number],
  ofDates: [Date],
  ofBuffer: [Buffer],
  ofBoolean: [Boolean],
  ofMixed: [Schema.Types.Mixed],
  ofObjectId: [Schema.Types.ObjectId],
  ofArrays: [[]],
  ofArrayOfNumbers: [[Number]],
  nested: {
    stuff: { type: String, lowercase: true, trim: true }
  },
  map: Map,
  mapOfString: {
    type: Map,
    of: String
  }
})

// example use

var Thing = mongoose.model('Thing', schema);

var m = new Thing;
m.name = 'Statue of Liberty';
m.age = 125;
m.updated = new Date;
m.binary = Buffer.alloc(0);
m.living = false;
m.mixed = { any: { thing: 'i want' } };
m.markModified('mixed');
m._someId = new mongoose.Types.ObjectId;
m.array.push(1);
m.ofString.push("strings!");
m.ofNumber.unshift(1,2,3,4);
m.ofDates.addToSet(new Date);
m.ofBuffer.pop();
m.ofMixed = [1, [], 'three', { four: 5 }];
m.nested.stuff = 'good';
m.map = new Map([['key', 'value']]);
m.save(callback);

Screenshots

Authors

• @rohit
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