Author: John Au-Yeung

Sometimes, we want to convert string to ObjectId with Node.js Mongoose.

In this article, we’ll look at how to convert string to ObjectId with Node.js Mongoose.

How to convert string to ObjectId with Node.js Mongoose?

To convert string to ObjectId with Node.js Mongoose, we can use the mongoose.Types.ObjectId method.

For instance, we write

const mongoose = require('mongoose');
const id = mongoose.Types.ObjectId('4edd40c86762e0fb12000003');

to call mongoose.Types.ObjectId with the ObjectId string to convert the string to an ObjectId.

Conclusion

To convert string to ObjectId with Node.js Mongoose, we can use the mongoose.Types.ObjectId method.

Sometimes, we want to replace a string in a file with Node.js.

In this article, we’ll look at how to replace a string in a file with Node.js.

How to replace a string in a file with Node.js?

To replace a string in a file with Node.js, we can use the readFile and writeFile method.

For instance, we write

const fs = require('fs')

fs.readFile(someFile, 'utf8', (err, data) => {
  if (err) {
    return console.log(err);
  }
  const result = data.replace(/string to be replaced/g, 'replacement');

  fs.writeFile(someFile, result, 'utf8', (err) => {
    if (err) {
      return console.log(err);
    }
  });
});

to call fs.readFile at path someFile.

And we read it as 'utf8 encoded file.

In the callback we pass into readFile, we get the read file content from data.

Then we call data.replace with a regex that matches the text we want to replace and replace them with 'replacement'.

Next, we call fs.writeFile to write the new result to path someFile.

Conclusion

To replace a string in a file with Node.js, we can use the readFile and writeFile method.

Sometimes, we want to read a file in Node.js.

In this article, we’ll look at how to read a file in Node.js.

How to read a file in Node.js?

To read a file in Node.js, we can use the fs.readFile method.

For instance, we write

const fs = require('fs')
const path = require('path')
const filePath = path.join(__dirname, 'start.html');

fs.readFile(filePath, {
  encoding: 'utf-8'
}, (err, data) => {
  if (!err) {
    console.log(data);
  } else {
    console.log(err);
  }
});

to call fs.readFile with the path of the file to read, an object with encoding to read the file with the given encoding, and a callback that has the read file data when the file is read.

We read the file at filePath as a text file encoded with 'utf-8'.

And then we get the file data from data.

If err is set, that means there’s an error when reading the file.

Conclusion

To read a file in Node.js, we can use the fs.readFile method.

Sometimes, we want to read from stdin line by line in Node.

In this article, we’ll look at how to read from stdin line by line in Node.

How to read from stdin line by line in Node?

To read from stdin line by line in Node, we can use the readline module.

To use it, we write

const readline = require('readline');
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  terminal: false
});

rl.on('line', (line) => {
  console.log(line);
})

to call readline.createInterface to return an object that lets us read the stdin by setting input to process.stdin.

Then when stdin updates, the 'line' event is emitted and we listen to the update with

rl.on('line', (line) => {
  console.log(line);
})

line has the stdin input value

Conclusion

To read from stdin line by line in Node, we can use the readline module.

Sometimes, we want to get all registered routes in Express.

In this article, we’ll look at how to get all registered routes in Express.

How to get all registered routes in Express?

To get all registered routes in Express, we can use the app._router.stack property.

For instance, we write

app._router.stack.forEach((r) => {
  if (r?.route?.path){
    console.log(r?.route?.path)
  }
})

to loop through the array returned by app._router.stack, which has all the routes in an array.

We get the path of each route from r.route.path.

Conclusion

To get all registered routes in Express, we can use the app._router.stack property.