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Version: 10.9.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 (or LocalizedText) 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.

Dynamic configuration

Many components allow the user to build dynamic configurations. Such configurations 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.

To achieve dynamic configurations logic, Back-Kit components use handlebars syntax and embed a web component property 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 configuration such

"user": "{{}}"

would be equivalent to

"user": ""


Custom helpers to be used in conjunction with handlebars are provided, most components that allow dynamic configurations support them.


rawObject allows to avoid to stringify dynamic values within a configuration.

"url": "/url",
"method": "POST",
"body": "{{rawObject data}}"

rawObject signals that the provided dynamic value (data in this case) should not be stringified. So, with input data:

"data": {
"name": "Joe",
"surname": "Smith"

the example is equivalent to:

"url": "/url",
"method": "POST",
"body": {
"name": "Joe",
"surname": "Smith"


rawObjectOrEmptyStr is equivalent to rawObject but, if the input value is not defined, an empty string will be put in place of the dynamic configuration.


nFormat allows to format numeric values specifying number of decimal places, decimal separator, group separator.

For instance, given the dynamic configuration:

"amount1": "$ {{nFormat '2.,' value}}",
"amount2": "$ {{nFormat '4.,' value}}",
"amount3": "$ {{nFormat '.,' value}}",
"amount4": "$ {{nFormat '.' value}}",
"amount5": "$ {{nFormat '' value}}"

and input data:

"value": 7654.321

the resulting configuration is:

"amount1": "7,654.32",
"amount2": "7,654.3210",
"amount3": "7,654.321",
"amount4": "7654.321",
"amount5": "7654.321"

Template - ConfigMap

Some components allow to specify an object with fields template-configMap instead of a value for their dynamically configurable properties.

"command": {
"template": "{{color}}",
"configMap": {
"red": "stop",
"yellow": "slow-down",
"$default": "go"

The value of template is matched against keys of configMap. On the first match, the corresponding value in configMap is used as value for the dynamic variable.

For instance, with context

"color": "red"

the above example is equivalent to:

"command": "stop"

$default key in configMap can be specified, and is used if no other configMap key matches template.

Extracting data from URL - UrlMask

Some components may expose properties that allow to configure a urlMask. This leverages path-to-regexp syntax to convert a string input (or mask) into a regular expression to be matched against the current URL, allowing to extract information from it, making it availbale in dynamic configurations.

urlMasks allow to specify masks for the pathname and search fields of window.location.

type UrlMask = string | {
pathname?: string,
search?: string

If urlMask is a string, it is matched against both pathname and search fields.


A urlMask such as

"urlMask": {
"pathname": "/path-name/:field1/:field2",
"search": "\\?pageSize=:pSize&sortDirection=:sDirection"

matched againsta a window.location like

"pathname": "/path-name/field-1/field-2",
"search": "?pageSize=25&sortDirection=descend"

will produce as output

"path": "/path-name/field-1/field-2",
"params": {
"field1": "field-1",
"field2": "field-2"

from pathname and

"path": "?pageSize=25&sortDirection=descend",
"params": {
"pSize": "25",
"sDirection": "descend"

from search.

Some components may allow to ignore part of the URL using wildcards, "(.*)". For instance:

"urlMask": "\\?pageNumber=:myPageNumber&pageNumber=(.*)"

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., "equal", "includeSome", ...)
  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. If a DataSchema should be filtered only according with a subset of available operators, a configuration key it available within the field filtersOptions. The key availableOperators is an array of string which, if defined, enables only explicitly selected operators on the given field.

Filter Operators

Filter operators can be selected from the following list:

type FilterOperator = |
'equal' |
'exists' |
'notEqual' |
'greater' |
'greaterEqual' |
'less' |
'lessEqual' |
'regex' |
'includeSome' |
'includeAll' |
'includeExactly' |
'notIncludeAny' |
'between' |
'notBetween' |
'hasLengthEqual' |
'hasLengthGreaterEqual' |

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

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