# Class: Value

## LuCI.form. Value

The `Value` class represents a simple one-line form input using the `LuCI.ui.Textfield` or - in case choices are added - the `LuCI.ui.Combobox` class as underlying widget.

#### new LuCI.form.Value(form, section, option, title, description)

form.js, line 3190

  Name | Type | Description
  --- | --- | ---
  `form` | LuCI.form.Map | LuCI.form.JSONMap | The configuration form this section is added to. It is automatically passed by `option()` or `taboption()` when adding the option to the section.
  `section` | LuCI.form.AbstractSection | The configuration section this option is added to. It is automatically passed by `option()` or `taboption()` when adding the option to the section.
  `option` | string | The name of the UCI option to map.
  `title` | string | optional The title caption of the option element.
  `description` | string | optional The description text of the option element.

### Extends

- LuCI.form.AbstractValue

### Members

#### passwordboolean

  If set to `true`, the field is rendered as password input, otherwise as plain text input.

  Default Value:
    - false

#### placeholderstring

  Set a placeholder string to use when the input field is empty.

  Default Value:
    - null

#### datatypestring

  Specifies a datatype constraint expression to validate input values against. Refer to `LuCI.validation` for details on the format.

  If the user entered input does not match the datatype validation, the option element is marked as invalid.

  Default Value:
    - null

#### default*

  Sets a default value to use when the underlying UCI option is not set.

  Default Value:
    - null

#### editableboolean

  Mark grid section option element as editable.

  Options which are displayed in the table portion of a `GridSection` instance are rendered as readonly text by default. By setting the `editable` property of a child option element to `true`, that element is rendered as full input widget within its cell instead of a text only preview.

  This property has no effect on options that are not children of grid section elements.

  Default Value:
    - false

#### modalonlyboolean

  Move grid section option element into the table, the modal popup or both.

  If this property is `null` (the default), the option element is displayed in both the table preview area and the per-section instance modal popup of a grid section. When it is set to `false` the option is only shown in the table but not the modal popup. When set to `true`, the option is only visible in the modal popup but not the table.

  This property has no effect on options that are not children of grid section elements.

  Default Value:
    - null

#### onchangefunction

  Register a custom value change handler.

  If this property is set to a function value, the function is invoked whenever the value of the underlying UI input element is changing.

  The invoked handler function will receive the DOM click element as first and the underlying configuration section ID as well as the input value as second and third argument respectively.

  Default Value:
    - null

#### optionalboolean

  If set to `true`, the underlying ui input widget is allowed to be empty, otherwise the option element is marked invalid when no value is entered or selected by the user.

  Default Value:
    - false

#### readonlyboolean

  Make option element readonly.

  This property defaults to the readonly state of the parent form element. When set to `true`, the underlying widget is rendered in disabled state, means its contents cannot be changed and the widget cannot be interacted with.

  Default Value:
    - false

#### rmemptyboolean

  If set to `false`, the underlying option value is retained upon saving the form when the option element is disabled due to unsatisfied dependency constraints.

  Default Value:
    - true

#### uciconfigstring

  Override the UCI configuration name to read the option value from.

  By default, the configuration name is inherited from the parent Map. By setting this property, a deviating configuration may be specified.

  The default is null, means inheriting from the parent form.

  Default Value:
    - null

#### ucioptionstring

  Override the UCI option name to read the value from.

  By default, the elements name, which is passed as third argument to the constructor, is used as UCI option name. By setting this property, a deviating UCI option may be specified.

  The default is null, means using the option element name.

  Default Value:
    - null

#### ucisectionstring

  Override the UCI section name to read the option value from.

  By default, the section ID is inherited from the parent section element. By setting this property, a deviating section may be specified.

  The default is null, means inheriting from the parent section.

  Default Value:
    - null

#### validatefunction

  Specifies a custom validation function to test the user input for validity. The validation function must return `true` to accept the value. Any other return value type is converted to a string and displayed to the user as validation error message.

  If the user entered input does not pass the validation function, the option element is marked as invalid.

  Default Value:
    - null

#### widthnumber string

  Override the cell width of a table or grid section child option.

  If the property is set to a numeric value, it is treated as pixel width which is set on the containing cell element of the option, essentially forcing a certain column width. When the property is set to a string value, it is applied as-is to the CSS `width` property.

  This property has no effect on options that are not children of grid or table section elements.

  Default Value:
    - null

### Methods

#### inherited append(element)

form.js, line 210

  Add another form element as children to this element.

  Name | Type | Description
  --- | --- | ---
  `element` | AbstractElement | The form element to add.

#### inherited cbid(section_id){string}

form.js, line 1733

  Obtain the internal ID ("cbid") of the element instance.

  Since each form section element may map multiple underlying configuration sections, the configuration section ID is required to form a fully qualified ID pointing to the specific element instance within the given specific section.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Throws:

  Throws a `TypeError` exception when no `section_id` was specified.

  Type
    TypeError

  ##### Returns:

  Type | Description
  --- | ---
  string | Returns the element ID.

#### inherited cfgvalue(section_id){*}

form.js, line 1807

  Query the underlying configuration value.

  The default implementation of this method returns the cached return value of `load()`. It may be overwritten by user code to obtain the configuration value in a different way.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Throws:

  Throws a `TypeError` exception when no `section_id` was specified.

  Type
    TypeError

  ##### Returns:

  Type | Description
  --- | ---
  * | Returns the configuration value.

#### inherited depends(optionname_or_depends, optionvalue|RegExp)

form.js, line 1615

  Add a dependency contraint to the option.

  Dependency constraints allow making the presence of option elements dependant on the current values of certain other options within the same form. An option element with unsatisfied dependencies will be hidden from the view and its current value is omitted when saving.

  Multiple constraints (that is, multiple calls to `depends()`) are treated as alternatives, forming a logical "or" expression.

  By passing an object of name => value pairs as first argument, it is possible to depend on multiple options simultaneously, allowing to form a logical "and" expression.

  Option names may be given in "dot notation" which allows to reference option elements outside of the current form section. If a name without dot is specified, it refers to an option within the same configuration section. If specified as `configname.sectionid.optionname`, options anywhere within the same form may be specified.

  The object notation also allows for a number of special keys which are not treated as option names but as modifiers to influence the dependency constraint evaluation. The associated value of these special "tag" keys is ignored. The recognized tags are:

  - `!reverse`
    Invert the dependency, instead of requiring another option to be equal to the dependency value, that option should not be equal.
  - `!contains`
    Instead of requiring an exact match, the dependency is considered satisfied when the dependency value is contained within the option value.
  - `!default`
    The dependency is always satisfied

  Examples:

  - `opt.depends("foo", "test")`
    Require the value of `foo` to be `test`.
  - `opt.depends({ foo: "test" })`
    Equivalent to the previous example.
  - `opt.depends({ foo: /test/ })`
    Require the value of `foo` to match the regular expression `/test/`.
  - `opt.depends({ foo: "test", bar: "qrx" })`
    Require the value of `foo` to be `test` and the value of `bar` to be `qrx`.
  - `opt.depends({ foo: "test" })
    opt.depends({ bar: "qrx" })`
    Require either `foo` to be set to `test`, or the `bar` option to be `qrx`.
  - `opt.depends("test.section1.foo", "bar")`
    Require the "foo" form option within the "section1" section to be set to "bar".
  - `opt.depends({ foo: "test", "!contains": true })`
    Require the "foo" option value to contain the substring "test".

  Name | Type | Description
  --- | --- | ---
  `optionname_or_depends` | string | Object.<string, (string|RegExp)> | The name of the option to depend on or an object describing multiple dependencies which must be satified (a logical "and" expression).
  `optionvalue|RegExp` | string | When invoked with a plain option name as first argument, this parameter specifies the expected value. In case an object is passed as first argument, this parameter is ignored.

#### inherited formvalue(section_id){*}

form.js, line 1835

  Query the current form input value.

  The default implementation of this method returns the current input value of the underlying `LuCI.ui` widget. It may be overwritten by user code to handle input values differently.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Throws:

  Throws a `TypeError` exception when no `section_id` was specified.

  Type
    TypeError

  ##### Returns:

  Type | Description
  --- | ---
  * | Returns the current input value.

#### inherited getUIElement(section_id){LuCI.ui.AbstractElement|null}

form.js, line 1784

  Obtain the underlying `LuCI.ui` element instance.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Throws:

  Throws a `TypeError` exception when no `section_id` was specified.

  Type
    TypeError

  ##### Returns:

  Type | Description
  --- | ---
  LuCI.ui.AbstractElement | null | Returns the `LuCI.ui` element instance or `null` in case the form option implementation does not use `LuCI.ui` widgets.

#### inherited isActive(section_id){boolean}

form.js, line 1923

  Test whether the option element is currently active.

  An element is active when it is not hidden due to unsatisfied dependency constraints.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Returns:

  Type | Description
  --- | ---
  boolean | Returns `true` if the option element currently is active, otherwise it returns `false`.

#### inherited isValid(section_id){boolean}

form.js, line 1905

  Test whether the input value is currently valid.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Returns:

  Type | Description
  --- | ---
  boolean | Returns `true` if the input value currently is valid, otherwise it returns `false`.

#### inherited load(section_id){*|Promise.<*>}

form.js, line 1761

  Load the underlying configuration value.

  The default implementation of this method reads and returns the underlying UCI option value (or the related JavaScript property for `JSONMap` instances). It may be overwritten by user code to load data from nonstandard sources.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Throws:

  Throws a `TypeError` exception when no `section_id` was specified.

  Type
    TypeError

  ##### Returns:

  Type | Description
  --- | ---
  * | Promise.<*> | Returns the configuration value to initialize the option element with. The return value of this function is filtered through `Promise.resolve()` so it may return promises if overridden by user code.

#### inherited parse(section_id){Promise.<void>}

form.js, line 1964

  Parse the option element input.

  The function is invoked when the `parse()` method has been invoked on the parent form and triggers input value reading and validation.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Returns:

  Type | Description
  --- | ---
  Promise.<void> | Returns a promise resolving once the input value has been read and validated or rejecting in case the input value does not meet the validation constraints.

#### inherited remove(section_id)

form.js, line 2034

  Remove the corresponding value from the configuration.

  This function is invoked upon saving the parent form when the option element has been hidden due to unsatisfied dependencies or when the user cleared the input value and the option is marked optional.

  The default implementation simply removes the associated option from the UCI configuration (or the associated JavaScript object property in case of `JSONMap` forms). It may be overwritten by user code to implement alternative removal logic, e.g. to retain the original value.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

#### inherited render(){Node|Promise.<Node>}

form.js, line 3264

  Render the form element.

  The `render()` function recursively walks the form element tree and renders the markup for each element, returning the assembled DOM tree.

  ##### Returns:

  Type | Description
  --- | ---
  Node | Promise.<Node> | May return a DOM Node or a promise resolving to a DOM node containing the form element's markup, including the markup of any child elements.

#### inherited stripTags(input){string}

form.js, line 286

  Strip any HTML tags from the given input string.

  Name | Type | Description
  --- | --- | ---
  `input` | string | The input string to clean.

  ##### Returns:

  Type | Description
  --- | ---
  string | The cleaned input string with HTML removes removed.

#### inherited textvalue(section_id){string}

form.js, line 1859

  Obtain a textual input representation.

  The default implementation of this method returns the HTML escaped current input value of the underlying `LuCI.ui` widget. User code or specific option element implementations may overwrite this function to apply a different logic, e.g. to return `Yes` or `No` depending on the checked state of checkbox elements.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID

  ##### Throws:

  Throws a `TypeError` exception when no `section_id` was specified.

  Type
    TypeError

  ##### Returns:

  Type | Description
  --- | ---
  string | Returns the text representation of the current input value.

#### inherited titleFn(property, fmt_args){string|null}

form.js, line 320

  Format the given named property as title string.

  This function looks up the given named property and formats its value suitable for use as element caption or description string. It also strips any HTML tags from the result.

  If the property value is a string, it is passed to `String.format()` along with any additional parameters passed to `titleFn()`.

  If the property value is a function, it is invoked with any additional `titleFn()` parameters as arguments and the obtained return value is converted to a string.

  In all other cases, `null` is returned.

  Name | Type | Description
  --- | --- | ---
  `property` | string | The name of the element property to use.
  `fmt_args` | * | repeatable Extra values to format the title string with.

  ##### Returns:

  Type | Description
  --- | ---
  string | null | The formatted title string or `null` if the property did not exist or was neither a string nor a function.

#### value(key, value)

form.js, line 3255

  Add a predefined choice to the form option. By adding one or more choices, the plain text input field is turned into a combobox widget which prompts the user to select a predefined choice, or to enter a custom value.

  Name | Type | Description
  --- | --- | ---
  `key` | string | The choice value to add.
  `value` | Node | string | The caption for the choice value. May be a DOM node, a document fragment or a plain text string. If omitted, the `key` value is used as caption.

#### inherited write(section_id, formvalue)

form.js, line 2011

  Write the current input value into the configuration.

  This function is invoked upon saving the parent form when the option element is valid and when its input value has been changed compared to the initial value returned by `cfgvalue()`.

  The default implementation simply sets the given input value in the UCI configuration (or the associated JavaScript object property in case of `JSONMap` forms). It may be overwritten by user code to implement alternative save logic, e.g. to transform the input value before it is written.

  Name | Type | Description
  --- | --- | ---
  `section_id` | string | The configuration section ID
  `formvalue` | string | Array.<string> | The input value to write.