Portal can be used as standalone with any part of a Fluent app. The component should be under a FluentProvider in the tree to make sure that proper theming and RTL handling is available.

By default Portal will render content to document body

<FluentProvider>
  <Portal>Content rendered by default to Fluent's document.body</Portal>
</FluentProvider>

The mount location of the portal can be customized

const node = document.getElementById('customNode');

<Portal mountNode={node}>Render to a custom node in DOM</Portal>;

Styling

Portal renders React children directly to the default/configured DOM node. Therefore styling should be applied to the children by users directly.

Virtual parents

Out of order DOM elements can be problematic when using 'click outside' event listeners since you cannot rely on element.contains(event.target) because the Portal elements are out of DOM order.


const outerButtonRef = React.useRef();
const innerButtonRef = React.useRef();


<Portal>
  <div>
    <button ref={outerButtonRef}> Outer button </button>
    <Portal>
      <div>
        <button ref={innerButtonRef}> Inner button </button>
      </div>
    </Portal>
  </div>
</Portal>

// DOM output
<div>
  <button>Outer button</button>
</div>

<div>
  <button>Inner button</button>
</div>

// Let's add an event listener to 'dismss' the outer portal when clicked outside
// ⚠⚠⚠ This will always be called when clicking on the inner button
document.addEventListener((event) => {
  if (outerButtonRef.current.contains(event.target)) {
    dismissOuterPortal();
  }
})

When the above case is not required, using element.contains is perfectly fine. But nested cases should still be handled appropriately. We do this using the concept of virtual parents

Portal will make public 2 utilities that will only be used in cases where the user needs to know if an out of order DOM element will need to be used or not.

setVirtualParent - sets virtual parent. Portal uses this already internally.
elementContains - similar to element.contains but uses the virtual hierarchy as reference

Below shows what a virtual parent is

// Setting a virtual parent

const parent document.getElementById('parent')
const child document.getElement.ById('child');

child._virtual.parent = parent;

Portals will render a hidden span that will be the virtual parent, by nesting portals virtual parens will also be nested so that elementContains will work predictably.

<FluentProvider>
  <Portal id="portal-1" />
  <Portal id="portal-2" />
</FluentProvider>

DOM output:

<body>
  <div>
    {/* Virtual parent for portal*/}
    <span aria-hidden />
    {/* Virtual parent for portal*/}
    <span aria-hidden />
  </div>

  <div id="portal-1" class="theme-provider-0">
    {children}
  </div>
  <div id="portal-2" class="theme-provider-0">
    {children}
  </div>
</body>

<FluentProvider>
  <Portal id="portal-1">
    <Portal id="portal-2" />
  </Portal>
</FluentProvider>

DOM output:

<body>
  <div>
    {/* Virtual parent for outer portal*/}
    <span aria-hidden></span>
  </div>

  <div id="portal-1" class="theme-provider-0">
    {/* Virtual parent for inner portal*/}
    <span aria-hidden />
    {children}
  </div>
  <div id="portal-2" class="theme-provider-0">
    {children}
  </div>
</body>

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Package last updated on 28 Oct 2022

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Install

@fluentui/react-portal