Handling errors plays a major role in your application. In error situations, you want to know the details of the issue and how to solve it. When developing your app, you can create your own errors.
Errors in Node.js are extensible classes. This tutorial walks you through the creation of your own error class.
Node.js Series Overview
- Increase the Memory Limit for Your Process
- Why You Should Add “node” in Your Travis Config
- Create a PDF from HTML with Puppeteer and Handlebars
- Create Your Own Custom Error
- Extend Multiple Classes (Multi Inheritance)
- Get a File’s Created Date
- Get a File’s Last Modified/Updated Date
- Write a JSON Object to a File
- How to Create an Empty File
- Generate a Random Number in Range With JavaScript/Node.js
- How to Merge Objects
- Retrieve a Request’s IP Address in Node.js
- Detect the Node.js Version in a Running Process or App
- String Replace All Appearances
- Remove All Whitespace From a String in JavaScript
- Generate a Random String in Node.js or JavaScript
- Remove Extra Spaces From a String in JavaScript or Node.js
- Remove Numbers From a String in JavaScript or Node.js
- Get the Part Before a Character in a String in JavaScript or Node.js
- Get the Part After a Character in a String in JavaScript or Node.js
- How to Check if a Value is a String in JavaScript or Node.js
- How to Run an Asynchronous Function in Array.map()
- How to Reset and Empty an Array
- for…of vs. for…in Loops
- Clone/Copy an Array in JavaScript and Node.js
- Get an Array With Unique Values (Delete Duplicates)
- Sort an Array of Integers in JavaScript and Node.js
- Sort a Boolean Array in JavaScript, TypeScript, or Node.js
- Check If an Array Contains a Given Value in JavaScript or Node.js (Coming soon)
- Callback and Promise Support in your Node.js Modules
- Run Async Functions/Promises in Sequence
- Run Async Functions/Promises in Parallel
- Run Async Functions in Batches
- How to Fix “Promise resolver undefined is not a function” in Node.js or JavaScript
- Detect if Value Is a Promise in Node.js and JavaScript
Create an Error Class
Node.js comes with an Error class. This error class gives you the core functionality of errors, like capturing a stack trace and assigning context data.
You can extend Node’s error class to create your own errors. Here’s an example of a NotEnoughCoffee error:
not-enough-coffee-error.js
class NotEnoughCoffee extends Error {
constructor (message) {
super(message)
// assign the error class name in your custom error (as a shortcut)
this.name = this.constructor.name
// capturing the stack trace keeps the reference to your error class
Error.captureStackTrace(this, this.constructor);
// you may also assign additional properties to your error
this.isSleepy = true
}
}
module.exports = NotEnoughCoffee
The custom error extends the default Node.js error class. Setting the this.name property to the constructor’s name will reference NotEnoughCoffee in stack traces instead of the generic Error name.
Go ahead and add other class properties when needed. You can even add methods that are more helpful. Here’s an example:
class CoffeeNotFound extends Error {
constructor (message) {
super(message)
Error.captureStackTrace(this, this.constructor);
this.name = this.constructor.name
this.status = 404
}
statusCode() {
return this.status
}
}
module.exports = CoffeeNotFound
This CoffeeNotFound error could be an HTTP error. You may intercept the response and map the error’s status to the HTTP response status.
Throwing Errors
Import the custom error in your app and use it when necessary. Here’s a simple example that just throws the NotEnoughCoffee error:
'use strict'
const NotEnoughCoffee = require('./error')
throw new NotEnoughCoffee('Well, you may need another coffee :)')
The related error output on your terminal looks like this:
Custom errors are a good way to help your coworkers and other developers to know what’s wrong with the app configuration.
Enjoy coding & make it rock!