# <netui:hidden> Tag

Generates an HTML hidden tag with a given value.

## Syntax

<netui:hidden
[dataInput="string_or_expression_dataInput"]
dataSource="expression_datasource"
[tabindex="string_tabIndex"]
[tagId="string_tagId"] />

## Description

Generates an HTML hidden tag with a given value.

The `dataInput` attribute overrides the `dataSource` attribute for the input of the value. It allows a <netui:hidden> tag to read it's value from one place (whatever is referenced by the `dataInput` attribute) and submit the value to a new destination (whatever is referenced by the `dataSource` attribute). The `dataInput` attribute may take a String literal or a data binding expression.

## Attributes

dataInput | The dataInput attribute overrides the dataSource attribute for the input of the value. It allows a <netui:hidden> tag to read it's value from one place (whatever is referenced by the `dataInput` attribute) and return the value to a new destination (whatever is referenced by the `dataSource` attribute). This attribute may take a String literal or a data binding expression.
Required | Supports runtime expression evaluation | Data bindable
No | No | Read Only
dataSource | The `dataSource` attribute determines both (1) the source of populating data for the tag and (2) the object to which the tag submits data. For example, assume that the Controller file (= JPF file) contains a Form Bean with the property foo. Then the following <netui:textBox> tag will (1) draw populating data from the Form Bean's foo property and (2) submit user defined data to the same property. `<netui:textBox dataSource="{actionForm.foo}" />` The `dataSource` attribute takes either a data binding expression or the name of a Form Bean property. In the above example, `<netui:textBox dataSource="foo" />` would have the exactly same behavior. When the tag is used to submit data, the data binding expression must refer to a Form Bean property. In cases where the tag is not used to submit data, but is used for displaying data only, the data binding expression need not refer to a Form Bean property. For example, assume that myIterativeData is a member variable on the Controller file ( = JPF file). The following <netui-data:repeater> tag draws its data from myIterativeData. `<netui-data:repeater dataSource="{pageFlow.myIterativeData}">`
Required | Supports runtime expression evaluation | Data bindable
Yes | No | Read / Write
tabindex | The tabIndex of the rendered HTML tag. This attribute determines the position of the rendered HTML tag in the sequence of tags that the user may advance through by pressing the TAB key.
Required | Supports runtime expression evaluation | Data bindable
No | No | No
tagId | String value. Sets the `id` (or `name`) attribute of the rendered HTML tag. Note that the real id attribute rendered in the browser may be changed by the application container (for example, Portal containers may change the rendered id value to ensure the uniqueness of id's on the page). In this case, the real id rendered in the browser may be looked up through the JavaScript function getNetuiTagName( tagId, tag ). For example, assume that some tag's `tagId` attribute is set to `foo`.
        <netui:textBox tagId="foo" />
Then the following JavaScript function will return the real id attribute rendered in the browser:
        getNetuiTagName( "foo", this )
To get a <netui:form> element and all of its children elements in JavaScript, use the same JavaScript function `getNetuiTagName( tagId, tag )`. For example, assume that there is a <netui:form> whose tagId attribute is set to `bar`.
        <netui:form tagId="bar" >
Then the following JavaScript function will return the <netui:form> element and its children (packaged as an array).
        document[getNetuiTagName( "bar", this )]
To retreive the value entered into a <netui:textBox> within the <netui:form> tag, use the following JavaScript expression.
        document[getNetuiTagName("bar", this)][getNetuiTagName("foo", this)].value
The second parameter ensures that the JavaScript function begins its search within the correct Portlet scope. Pass the JavaScript keyword `this` as the second parameter. For detailed information on using the function `getNetuiTagName( tagId, tag )` see Using JavaScript in Page Flow and Portal Applications.
Required | Supports runtime expression evaluation | Data bindable
No | Yes | No

## Sample

In this sample, the <netui:hidden> gets it value from the Page Flow's hiddenValue property and writes its value (on submission of a <netui:form> tag that encloses it) to the Form Bean's hidden property.

          <netui:hidden dataSource="{actionForm.hidden}" dataInput="{pageFlow.hiddenValue}" />