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Need help cleaning up this code, which modifies the subdomain.

DeChamp on July 10, 2019

Goal would be to get one subdomain and swap it out for another. I feel there has to be a cleaner way to do this. help me out! var url = window.l...

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Kasey Speakman • Jul 10 '19 • Edited

var subdomainMatch = /^[^.]+\./;
var admin = window.location.host.replace(subdomainMatch, "admin.");

This is using a regex, but at least it is a small one.

op	meaning
`^`	line starts with
`[^`	any character except the following
`.`	the character `.`
`]`	end of character list
`+`	match one or more of the preceding (any character except `.`)
`\.`	match the character `.`

DeChamp • Jul 10 '19 • Edited

gorgeous! I love me some regex. I was trying to do this yesterday but going about it all wrong. I was trying to abstract out the last part of the domain. Should have made it easy on myself and just find/replace the subdomain! Thank you!

Daniel J Dominguez • Jul 10 '19 • Edited

Well, according to the documentation for slice, using a negative index will allow you start indexing from the end of the array rather than the beginning.
So domainParts.slice(domainParts.length - 2, domainParts.length) is equivalent to domainParts.slice(-2).
Another thing is that since admin is a constant, you can add that when you are concatenating the string rather than manipulating the array.

var url = window.location;

// example domain would have a subdomain so https://auth.domain.ext
var domain = url.host;

var subdomain = 'admin';
var mainDomain = domain.split('.').slice(-2).join('.');
var fullAdminDomain = url.protocol + '//' + subdomain + '.' + mainDomain;

Array.prototype.slice

DeChamp • Jul 10 '19

aww yes! nice!