# The visible binding

## Overview

The `visible` binding causes the associated DOM element to become hidden or visible according to the value you pass to the binding.

Example

    <div data-bind="visible: shouldShowMessage">
      You will see this message only when "shouldShowMessage" holds a true value.
    </div>

    var viewModel = {
      shouldShowMessage: fw.observable(true) // Message initially visible
    };
    viewModel.shouldShowMessage(false); // ... now it's hidden
    viewModel.shouldShowMessage(true); // ... now it's visible again

## Parameters

- Main parameter

  - When the parameter resolves to a false-like value (e.g., the boolean value `false`, or the numeric value `0`, or `null`, or `undefined`), the binding sets `yourElement.style.display` to `none`, causing it to be hidden. This takes priority over any display style you've defined using CSS.

  - When the parameter resolves to a true-like value (e.g., the boolean value `true`, or a non-`null` object or array), the binding removes the `yourElement.style.display` value, causing it to become visible.

    Note that any display style you've configured using your CSS rules will then apply (so CSS rules like `x { display:table-row }` work fine in conjunction with this binding).

  If this parameter is an observable value, the binding will update the element's visibility whenever the value changes. If the parameter isn't observable, it will only set the element's visibility once and will not update it again later.

- Additional parameters

  - None

## Controlling Visibility

You can also use a JavaScript function or arbitrary JavaScript expression as the parameter value. If you do, Footwork will run your function/evaluate your expression, and use the result to determine whether to hide the element.

For example,

    <div data-bind="visible: myValues().length > 0">
      You will see this message only when 'myValues' has at least one member.
    </div>

    var viewModel = {
      myValues: fw.observableArray([]) // Initially empty, so message hidden
    };
    viewModel.myValues.push("some value"); // Now visible