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Version: 8.9.x

Core concepts

Localization and i18n

Back-kit web components supports localization and internationalization. Component properties that in turn expose any kind of typography can be easily internationalized by passing a LocalizedString object containing specific translations according to ISO 639-1 codes.

"en": "house",
"fr": "maison",
"de": "haus",
"it": "casa",
"zh": "房子",
"ar": "منزل",

Fields that support i18n are marked through this guide as taking either string or LocalizedString as input type.


Many components allow the user to build dynamic queries. Such queries are really helpful when an event needs to be aware of situation-specific data, such as, while clicking a button onto a given table row, the event must be intertwined with data of that row. In general, dynamic query output compiles to a URL query part.

To achieve dynamic query logic, Back-Kit components use handlebars syntax and embed a web component property (often called query) to register a handlebar template. By default, a string is parsed by the handlebar parser without making any changes to it if no {{}}-syntax is present.

For instance, any Back-Kit component is aware of an authenticated user, if any, using the property currentUser. When currentUser has property email with value, a query with syntax

"user": "{{}}"

would compile to a string "".


Notice that handlebar compilation is always URL encoded.

Rather complex queries can be built using handlebars while combining it with raw syntax. Queries are also well suited to transfer state between pages.

A standard interface is available for encoding external links and href. This interface can be found as building block of several Back-Kit web components properties.

A basic external href link rendering in a browser new tab can be implemented as

"href": "",
"target": "_blank",
"icon": "fas fa-link"

Property href can either be absolute or relative, target can be picked amongst _blank, _self, _parent, _top: most commonly either an href renders into the same window with _self or it opens a new tab with _blank.

The icon properties allow to attach a Fontawesome fas or far icon when the link is rendered by a component which support this interface.

A web component that contains state or data might implement dynamic queries. In this case the href can be enriched with query parameters that are bound to the internal state of the component that the user is interacting with. Suppose the user with email is in session, then the following link

"href": "customers",
"query": {
"name": "John",
"createdBy": "admin|{{}}"

renders the dynamic link ./ingredients?name=John&

Shared Properties

Back-kit web components always retain an eventBus property. For this reason it is not listed on components. Moreover, configuration should never interact with this property directly, since it is injected by the element-composer on configuration parsing. Anyway components mark this property as immutable and JavaScript should not be able to tamper with it.


Back-kit web components refine data queries and data views using filters. Filters can be used to enrich a change-query and are building blocks of many tag properties. A filter is made of three required build blocks:

  1. property: the unique identifier of the property they filter
  2. operator: the operator used to filter (i.e., "equals", "includes", ...)
  3. value: the value or the regex pattern (where it applies) to filter for

Operators and values vary according to the property type which is set by the data schema.

File Management

Upload and management of files related to a record is handled by 3 components that interact together:

  • bk-file-client
  • bk-file-manager
  • bk-form-drawer

Any file property can be specified in the data schema as:

type: 'object'
format: 'file'

Currently only "single-file" properties are supported

Once a file property is specified in the data schema and its form field is touched the routine will be as follows:

  1. bk-form-drawer fires a create-data-with-file/update-data-with-file event containing the full payload and list of all the file properties that have to be uploaded
  2. The above event is handled by the file-manager which will proceed to fire an upload-file event for each file in the list
  3. The file-client handles the upload-file event by taking its payload (the file object) and upload it to the file service, upon success will fire an uploaded-file event, containing the fileId to be linked to the record
  4. The file-manager listens for uploaded-file events and links each file to the proper record key, replacing it in the payload that was provided by the bk-form-drawer
  5. Once all the files have been uploaded, the file-manager fires a create-data/update-data event with the full payload as the bk-form-drawer would have, with the file objects correctly linked

Upon failure while uploading one file, any new file that was being uploaded in the same transaction (i.e. creating a new record that contained multiple file properties), will be deleted, even if already uploaded, because the final create/update of the record will not be performed


By design, any file that is unlinked from the record when updating an entry, isn't deleted from the file-service