use-visibility/useVisibility.js

React hook to check component visibility

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = useVisibility;

var _react = require("react");

var _throttle = _interopRequireDefault(require("./throttle"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { "default": obj }; }

function _slicedToArray(arr, i) { return _arrayWithHoles(arr) || _iterableToArrayLimit(arr, i) || _unsupportedIterableToArray(arr, i) || _nonIterableRest(); }

function _nonIterableRest() { throw new TypeError("Invalid attempt to destructure non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method."); }

function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o === "string") return _arrayLikeToArray(o, minLen); var n = Object.prototype.toString.call(o).slice(8, -1); if (n === "Object" && o.constructor) n = o.constructor.name; if (n === "Map" || n === "Set") return Array.from(o); if (n === "Arguments" || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(n)) return _arrayLikeToArray(o, minLen); }

function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) { arr2[i] = arr[i]; } return arr2; }

function _iterableToArrayLimit(arr, i) { if (typeof Symbol === "undefined" || !(Symbol.iterator in Object(arr))) return; var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

function _arrayWithHoles(arr) { if (Array.isArray(arr)) return arr; }

function useVisibility() {
  var offset = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
  var throttleMilliseconds = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 100;

  var _useState = (0, _react.useState)(false),
      _useState2 = _slicedToArray(_useState, 2),
      isVisible = _useState2[0],
      setIsVisible = _useState2[1];

  var currentElement = /*#__PURE__*/(0, _react.createRef)();
  var onScroll = (0, _throttle["default"])(function () {
    if (!currentElement.current) {
      setIsVisible(false);
      return;
    }

    var top = currentElement.current.getBoundingClientRect().top;
    setIsVisible(top - offset <= window.innerHeight);
  }, throttleMilliseconds);
  (0, _react.useEffect)(function () {
    document.addEventListener("scroll", onScroll, true);
    return function () {
      return document.removeEventListener("scroll", onScroll, true);
    };
  });
  return [isVisible, currentElement];
}