Category: JavaScript

To write file if parent folder doesn’t exist with Node.js, we use the fs-extra module.

For instance, we write

const fs = require("fs-extra");
const file = "/tmp/this/path/does/not/exist/file.txt";

fs.outputFile(file, "hello!", (err) => {
  console.log(err);

  fs.readFile(file, "utf8", (err, data) => {
    console.log(data);
  });
});

to call the outputFile method to write 'hello!' to the file path.

And then we call readFile to read the file path in the outputFile callback.

To write loops for promise with JavaScript, we use async and await.

For instance, we write

const myFunction = async () => {
  //...
  while (condition) {
    const res = await db.getUser(email);
    logger.log(res);
  }
};

to use a while loop in the myFunction function.

In it, we use await to wait for the promise to resolve and return the value before we move to the next iteration.

To add timestamps to all console messages with Node.js, we use the log-timestamp package.

To install it, we run

npm install log-timestamp

Then we use it by writing

require("log-timestamp");
console.log("After log-timestamp");

to require the log-timestamp package.

And then we call console.log to prepend the timestamp to the log message.

To use Mongoose with TypeScript, we define interfaces for our schemas.

For instance, we write

export interface IUser extends mongoose.Document {
  name: string;
  somethingElse?: number;
}

export const UserSchema = new mongoose.Schema({
  name: { type: String, required: true },
  somethingElse: Number,
});

const User = mongoose.model<IUser>("User", UserSchema);
export default User;

to define the IUser interface that inherits from the mongoose.Document interface.

Then we create the UserSchema with mongoose.Schema with a few fields in the object we call it with.

Next, we call model to map the 'User‘ table to UserSchema.

We set the type of the fields to match the IUser with the generic type argument.

To fix E: Unable to locate package npm error with JavaScript, we installk the npm package.

First, we run

sudo apt-get update
sudo apt-get upgrade

to get the latest package data with sudo apt-get update and update installed packages with sudo apt-get upgrade.

Then we run

sudo apt-get install npm

to install the npm package.