flip

A visibility optimizer that changes the placement of the floating element in order to keep it in view, with the ability to flip to any placement.

This is useful to prevent the floating element from overflowing on the main axis of its placement.

Usage

import {computePosition, flip} from '@floating-ui/dom';
 
computePosition(referenceEl, floatingEl, {
  middleware: [flip()],
});

import {computePosition, flip} from '@floating-ui/dom';
 
computePosition(referenceEl, floatingEl, {
  middleware: [flip()],
});

Options

These are the options you can pass to flip()flip().

interface Options extends DetectOverflowOptions {
  mainAxis?: boolean;
  crossAxis?: boolean;
  fallbackAxisSideDirection?: 'none' | 'start' | 'end';
  flipAlignment?: boolean;
  fallbackPlacements?: Array<Placement>;
  fallbackStrategy?: 'bestFit' | 'initialPlacement';
}

interface Options extends DetectOverflowOptions {
  mainAxis?: boolean;
  crossAxis?: boolean;
  fallbackAxisSideDirection?: 'none' | 'start' | 'end';
  flipAlignment?: boolean;
  fallbackPlacements?: Array<Placement>;
  fallbackStrategy?: 'bestFit' | 'initialPlacement';
}

mainAxis

default: truetrue

This is the main axis in which overflow is checked to perform a flip. By disabling this, it will ignore overflow.

• y-axis for 'top''top' and 'bottom''bottom' placements
• x-axis for 'left''left' and 'right''right' placements

flip({
  mainAxis: false,
});

flip({
  mainAxis: false,
});

crossAxis

default: truetrue

This is the cross axis in which overflow is checked to perform a flip, the axis perpendicular to mainAxismainAxis. By disabling this, it will ignore overflow.

flip({
  crossAxis: false,
});

flip({
  crossAxis: false,
});

fallbackAxisSideDirection

default: 'none''none'

Whether to allow fallback to the opposite axis if no placements along the preferred placement axis fit, and if so, which side direction along that axis to choose. If necessary, it will fallback to the other direction.

• 'none''none' signals that no fallback to the opposite axis should take place.
• 'start''start' represents 'top''top' or 'left''left'.
• 'end''end' represents 'bottom''bottom' or 'right''right'.

For instance, by default, if the initial placementplacement is set to 'right''right', then the placements to try (in order) are:

['right', 'left']['right', 'left']

On a narrow viewport, it’s possible or even likely that neither of these will fit.

By specifying a string other than 'none''none', you allow placements along the perpendicular axis of the initial placement to be tried. The direction determines which side of placement is tried first:

flip({
  fallbackAxisSideDirection: 'start',
});

flip({
  fallbackAxisSideDirection: 'start',
});

The above results in: ['right', 'left', 'top', 'bottom']['right', 'left', 'top', 'bottom'].

flip({
  fallbackAxisSideDirection: 'end',
});

flip({
  fallbackAxisSideDirection: 'end',
});

The above results in: ['right', 'left', 'bottom', 'top']['right', 'left', 'bottom', 'top'].

As an example, if you’d like a tooltip that has a placement of 'right''right' to be placed on top on mobile (assuming it doesn’t fit), then you’d use 'start''start'. For an interactive popover, you likely want to use 'end''end' so it’s placed on the bottom, closer to the user’s fingers.

In each of the following demos, the placementplacement is 'right''right'.

Combining with shift

If shift()shift() is in use in the middleware array, you may desire to disable crossAxiscrossAxis overflow checking, which will allow shift()shift() to perform its work without falling back to the opposite axis (therefore preserving the original axis as best as possible):

const middleware = [
  flip({
    fallbackAxisSideDirection: 'start',
    crossAxis: false,
  }),
  shift(),
];

const middleware = [
  flip({
    fallbackAxisSideDirection: 'start',
    crossAxis: false,
  }),
  shift(),
];

If your placement is not edge aligned, disabling it is usually a good choice.

flipAlignment

default: truetrue

When an alignment is specified, e.g. 'top-start''top-start' instead of just 'top''top', this will flip to 'top-end''top-end' if startstart doesn’t fit.

flip({
  flipAlignment: false,
});

flip({
  flipAlignment: false,
});

When using this with the shift()shift() middleware, ensure flip()flip() is placed before shift()shift() in your middleware array. This ensures the flipAlignmentflipAlignment logic can act before shift()shift()’s does.

fallbackPlacements

default: [oppositePlacement][oppositePlacement]

This describes an explicit array of placements to try if the initial placementplacement doesn’t fit on the axes in which overflow is checked.

flip({
  fallbackPlacements: ['right', 'bottom'],
});

flip({
  fallbackPlacements: ['right', 'bottom'],
});

In the above example, if placementplacement is set to 'top''top', then the placements to try (in order) are:

['top', 'right', 'bottom']['top', 'right', 'bottom']

fallbackStrategy

default: 'bestFit''bestFit'

When no placements fit, then you’ll want to decide what happens. 'bestFit''bestFit' will use the placement which fits best on the checked axes. 'initialPlacement''initialPlacement' will use the initial placementplacement specified.

flip({
  fallbackStrategy: 'initialPlacement',
});

flip({
  fallbackStrategy: 'initialPlacement',
});

…detectOverflowOptions

All of detectOverflow’s options can be passed. For instance:

flip({
  padding: 5, // 0 by default
});

flip({
  padding: 5, // 0 by default
});

Deriving options from state

You can derive the options from the middleware lifecycle state:

flip((state) => ({
  padding: state.rects.reference.width,
}));

flip((state) => ({
  padding: state.rects.reference.width,
}));

Final placement

The placement returned from the function is always the final one, not necessarily the one you passed in as the “preferred” one.

computePosition(referenceEl, floatingEl, {
  placement: 'bottom',
  middleware: [flip()],
}).then(({placement}) => {
  console.log(placement); // 'top' or 'bottom'
});

computePosition(referenceEl, floatingEl, {
  placement: 'bottom',
  middleware: [flip()],
}).then(({placement}) => {
  console.log(placement); // 'top' or 'bottom'
});

Conflict with autoPlacement

flip()flip() and autoPlacement()autoPlacement() cannot be used together inside the same middleware array, make sure you choose only one of them to use.

The reason is they both try to perform work on the placement but with opposing strategies. Therefore, they will continually try to change the result or work of the other one, leading to a reset loop.

• flip()flip() — Uses a fallback “no space” strategy. Ensures the preferred placement is kept unless there is no space left.
• autoPlacement()autoPlacement() — Uses a primary “most space” strategy. Always chooses the placement with the most space available.