node_modules/popper.js/src/modifiers/hide.js

import isModifierRequired from '../utils/isModifierRequired';
import find from '../utils/find';

/**
 * @function
 * @memberof Modifiers
 * @argument {Object} data - The data object generated by update method
 * @argument {Object} options - Modifiers configuration and options
 * @returns {Object} The data object, properly modified
 */
export default function hide(data) {
  if (!isModifierRequired(data.instance.modifiers, 'hide', 'preventOverflow')) {
    return data;
  }

  const refRect = data.offsets.reference;
  const bound = find(
    data.instance.modifiers,
    modifier => modifier.name === 'preventOverflow'
  ).boundaries;

  if (
    refRect.bottom < bound.top ||
    refRect.left > bound.right ||
    refRect.top > bound.bottom ||
    refRect.right < bound.left
  ) {
    // Avoid unnecessary DOM access if visibility hasn't changed
    if (data.hide === true) {
      return data;
    }

    data.hide = true;
    data.attributes['x-out-of-boundaries'] = '';
  } else {
    // Avoid unnecessary DOM access if visibility hasn't changed
    if (data.hide === false) {
      return data;
    }

    data.hide = false;
    data.attributes['x-out-of-boundaries'] = false;
  }

  return data;
}