Ghost/ghost/admin/app/services/slug-generator.js

import RSVP from 'rsvp';
import Service, {inject as service} from '@ember/service';
import classic from 'ember-classic-decorator';
import {slugify} from '@tryghost/string';

const {resolve} = RSVP;

@classic
export default class SlugGeneratorService extends Service {
    @service ghostPaths;
    @service ajax;

    generateSlug(slugType, textToSlugify) {
        let url;

        if (!textToSlugify) {
            return resolve('');
        }

        // We already do a partial slugify at the client side to prevent issues with Pro returning a 404 page because of invalid (encoded) characters (a newline, %0A, for example)
        url = this.get('ghostPaths.url').api('slugs', slugType, encodeURIComponent(slugify(textToSlugify)));

        return this.ajax.request(url).then((response) => {
            let [firstSlug] = response.slugs;
            let {slug} = firstSlug;

            return slug;
        });
    }
}