Validating email is simple, right? Just throw a regex at it? Well it’s not as simple as you might think. The RFC Spec (Page 27 of this monster, if you’re interested) is clear as mud on what constitutes a valid email.

With all the special characters and conditions of what can go before and after the @ , a regex to validate emails accurately would be incomprehensable at best.

If you’d like to find out more about why email validation sucks check out this article, for now let’s move along.

Surely this is something other people have dealt with though, what about a library? Well, they do exist, however, we want to really validate an email. This is most likely either a core communication or authentication property. Libraries can do more than a regex, but many lack more advanced checks against actual resources, looking at email services and their own history of valid domains/emails.

Using a Service for Validation

We want to know if an email is valid, but regex is tricky and libraries are limited. This is where validation services come in handy. Mailgun’s API for email validation is a wonderful option. It will check a number of things for us:

General syntax based on RFC

DNS validation

Spell check (common email services)

Service Provider checking

Not only will it take care of the general syntax (what we would use a hyper-complex regex for) but it will make “best-attempt” tries at checking for common errors and valid domains.

So, you may be asking yourself what this looks like. Typically validation is a synchronous task but we’re going to call an API to make this work. This is where Obey makes things simple. The promise-first design allows it to handle async and sync requests exactly the same. But what does this look like?

We start with a simple type definition. Using Obey and request-promise we’ll hit the API and handle the results:

const obey = require ( 'obey' ) const rp = require ( 'request-promise' ) // Our API key (use the public key for validation) const mailgunKey = 'XXXXX-YYYY-ZZZZZZZ' obey . type ( 'mailgunEmail' , ( context ) => { // Hit the API return rp ({ uri : ` https : //api:${mailgunKey}@api.mailgun.net/v3/address/validate`, qs : { address : context . value }, json : true }). then (( result ) => { // Handle validation errors if ( ! result . is_valid ) { context . fail ( context . value + ' is an invalid email' ) } }) })

Now when we define a model or rule we can use the mailgunEmail type and validation against the Mailgun API will occur. If the address returns invalid it will call context.fail resulting in a ValidationError .

Expanding the Concept

The above is a fairly straightforward example. However, Mailgun isn’t your only option for email validation, and there are a myriad of great validation APIs for other data types like phone numbers and addresses. The code could easily be modified to perform all sorts of asynchronous validation.

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