Author: John Au-Yeung

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.

To wait N seconds before continuing to the next line with Puppeteer and JavaScript, we use the waitForTimeout method.

For instance, we write

await page.waitForTimeout(4000);

to call page.waitForTimeout to pause the program for 4 seconds.

To detect CTRL+C in Node.js, we can listen for the SIGINT event.

For instance, we write

process.on("SIGINT", () => {
  console.log("Caught interrupt signal");

  if (shouldExit) {
    process.exit();
  }
});

to listen for the SIGIN event with process.on.

We call it with a callback that’s called when ctrl+c is pressed.

In it, we call process.exit to exit the program if shouldExit is true.

To fix AWS lambda API gateway error "Malformed Lambda proxy response" with JavaScript, we should return a response in the right format.

For instance, our response should have something like

{
  "isBase64Encoded": true,
  "statusCode": 200,
  "headers": { "headerName": "headerValue" },
  "body": "..."
}

The properties listed should be in the response JSON.

statusCode is the HTTP status code.

headers is an object with the response headers keys and values.

body is the response body.