Mongoose handle duplicate url slug - string

Question

I am storing url slugs from blog titles in MongoDB using Mongoose. So for instances when users enter the same blog title, I want to do it like how Wordpress handles it which is appending a number on the slug and increment it for every duplicates.
Example:
blog-title
blog-title-2
blog-title-3
Also when the slug evaluated from a blog title is blog-title-2 and there is already a blog-title-2 slug, it will be smart enough to append -2 at the back instead of incrementing the number. So it will be blog-title-2-2.
How do I implement that?

Answer 1

I managed to figure out how to implement it myself.
function setSlug(req, res, next) {
// remove special chars, trim spaces, replace all spaces to dashes, lowercase everything
var slug = req.body.title.replace(/[^\w\s]/gi, '').trim().replace(/\s+/g, '-').toLowerCase();
var counter = 2;
// check if there is existing blog with same slug
Blog.findOne({ slug: slug }, checkSlug);
// recursive function for checking repetitively
function checkSlug(err, existingBlog) {
if(existingBlog) { // if there is blog with the same slug
if(counter == 2) // if first round, append '-2'
slug = slug.concat('-' + counter++);
else // increment counter on slug (eg: '-2' becomes '-3')
slug = slug.replace(new RegExp(counter++ + '$', 'g'), counter);
Blog.findOne({ slug: slug }, checkSlug); // check again with the new slug
} else { // else the slug is set
req.body.slug = slug;
next();
}
};
}
I played around with Wordpress for a bit; publishing a lot of test blog posts with weird titles just to see how it handles the title conversion and I implemented the first step in converting the title according to my discoveries. Wordpress:
removes all special characters
trims away leading and ending spaces
converts remaining spaces to single dashes
lowercase everything

Answer 2

In your mongooese model you can give the field the unique option:
var post = new post({
slug: {
type: String,
unique: true
}
});
Then when you save it you can validate and know if the slug is not unique, in which case you can modify the slug:
var post = new post({ slug: "i-am-slug"});
var tempSlug = post.slug
var slugIsUnique = true;
car counter = 1;
do{
error = post.validateSync();
if(// not unique ){ //Make sure to only check for errors on post.slug here
slugIsUnique = false;
counter++;
tempSlug = post.slug + "-" + counter;
}
}while(!slugIsUnique)
post.slug = tempSlug;
post.save((err, post) => {
// check for error or do the usual thing
});
Edit:
This wont take blog-title-2 and output blog-title-2-2 but it will ouput blog-title-2-1 unless that already exists

Answer 3

I found the following code worked for me:
The general idea is to create an array of slugs you may potentially want to use and then use the MongoDB's $in query operator to determine if any of those slugs exist.
Note: The below solutions uses NPM's slugify. This is optional. I also use crytpo for randomizing since it has higher performance. Which is also optional.
private getUniqueSlug(title: string) {
// Returns a promise to allow async code.
return new Promise((resolve, reject) => {
const uniqueSlug: string = "";
// uses npm slugify. You can use whichever library you want or make your own.
const slug: string = slugify(title, { lower: true, strict: true });
// determines if slug is an ObjectID
const slugIsObjId: boolean = (ObjectId.isValid(slug) && !!slug.match(/^[0-9a-fA-F]{24}$/));
// creates a list of slugs (add/remove to your preference)
const slugs: string[] = [];
// ensures slug is not an ObjectID
slugIsObjId ? slugs.push(slug + "(1)") : slugs.push(slug);
slugs.push(slug + "(2)");
slugs.push(slug + "(3)");
slugs.push(slug + "(4)");
slugs.push(slug + "(5)");
// Optional. 3 random as fallback (crypto used to generate a random 4 character string)
for (let x = 0; x < 2; x++) {
slugs.push(slug + "(" + crypto.randomBytes(2).toString("hex") + ")");
}
// Uses a single find instance for performance purposes
// $in searches for all collections with a slug in slugs array above
const query: any = { slug: { $in: slugs } };
Collection.find(query, { slug: true }).then((results) => {
if (results) {
results.forEach((result) => {
slugs.every((s, si) => {
// If match found, remove from slugs since that slug ID is not valid.
if (s === result.slug) { slugs.splice(si, 1); return false; } else { return true; }
});
});
}
// returns first slug. Slugs are ordered by priority
if (slugs.length > 0) { resolve(slugs[0]); } else {
reject("Unable to generate a unique slug."); // Note: If no slug, then fails. Can use ObjectID as failsafe (nearly impossible).
}
}, (err) => {
reject("Find failed");
});
});
}