Ghost/ghost/admin/app/components/gh-url-preview.js

import Ember from 'ember';
/*
Example usage:
{{gh-url-preview prefix="tag" slug=theSlugValue tagName="p" classNames="description"}}
*/
export default Ember.Component.extend({
    classNames: 'ghost-url-preview',
    prefix: null,
    slug: null,

    config: Ember.inject.service(),

    url: Ember.computed('slug', function () {
        // Get the blog URL and strip the scheme
        var blogUrl = this.get('config.blogUrl'),
            noSchemeBlogUrl = blogUrl.substr(blogUrl.indexOf('://') + 3), // Remove `http[s]://`

            // Get the prefix and slug values
            prefix = this.get('prefix') ? this.get('prefix') + '/' : '',
            slug = this.get('slug') ? this.get('slug') + '/' : '',

            // Join parts of the URL together with slashes
            theUrl = noSchemeBlogUrl + '/' + prefix + slug;

        return theUrl;
    })
});