react-component-lazy-loader/lib/index.js

A package which lazily loads it's children components based on viewport visibility of the component. Useful in lazyloading images or any other custom component.

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

var _react = require('react');

var React = _interopRequireWildcard(_react);

var _reactDom = require('react-dom');

var _propTypes = require('prop-types');

var _lodash = require('lodash.throttle');

var _lodash2 = _interopRequireDefault(_lodash);

var _lodash3 = require('lodash.get');

var _lodash4 = _interopRequireDefault(_lodash3);

var _utils = require('./utils');

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

function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

var ReactComponentLazyLoader = function (_React$Component) {
  _inherits(ReactComponentLazyLoader, _React$Component);

  function ReactComponentLazyLoader(props) {
    _classCallCheck(this, ReactComponentLazyLoader);

    var _this = _possibleConstructorReturn(this, (ReactComponentLazyLoader.__proto__ || Object.getPrototypeOf(ReactComponentLazyLoader)).call(this, props));

    _this.setPlaceholderNodePosition = function () {
      var elementPos = _this.placeholderNode.getBoundingClientRect();
      _this.setState({
        distanceOfElementFromTop: elementPos.top,
        distanceOfElementFromLeft: elementPos.left
      });
    };

    _this.handleViewportChangeEvents = function () {
      var _this$props = _this.props,
          noLazyHorizontalScroll = _this$props.noLazyHorizontalScroll,
          wrapperID = _this$props.wrapperID;

      if (noLazyHorizontalScroll && _this.loadOnVerticalScroll()) {
        _this.setState({ renderLazyLoadedComponent: true });
        _this.removeEventListeners();
      } else if (wrapperID) {
        var wrapperNode = document.getElementById('' + wrapperID);
        if (_this.loadOnVerticalScroll() && _this.loadOnHorizontalScroll()) {
          _this.setState({ renderLazyLoadedComponent: true });
          _this.removeEventListeners(wrapperNode);
        }
        if (!_this.horizontalEventAdded) {
          wrapperNode.addEventListener('scroll', _this.handleWrapperScroll);
          wrapperNode.addEventListener('resize', _this.handleWrapperScroll);
          _this.horizontalEventAdded = true;
        }
      } else if (_this.loadOnVerticalScroll() && _this.loadOnHorizontalScroll()) {
        _this.setState({ renderLazyLoadedComponent: true });
        _this.removeEventListeners();
      }
    };

    _this.handleWrapperScroll = function () {
      var wrapperID = _this.props.wrapperID;
      var distanceOfElementFromLeft = _this.state.distanceOfElementFromLeft;

      var wrapperNode = document.getElementById('' + wrapperID);
      var scrollLeft = wrapperNode.scrollLeft;

      var loadOnHorizontalScroll = distanceOfElementFromLeft < window.innerWidth + scrollLeft;
      if (_this.loadOnVerticalScroll() && loadOnHorizontalScroll) {
        _this.setState({ renderLazyLoadedComponent: true });
        _this.removeEventListeners(wrapperNode);
      }
    };

    _this.addEventListeners = function () {
      window.addEventListener('resize', _this.handleViewportChangeEvents);
      window.addEventListener('scroll', _this.handleViewportChangeEvents);
    };

    _this.removeEventListeners = function (wrapperNode) {
      window.removeEventListener('resize', _this.handleViewportChangeEvents);
      window.removeEventListener('scroll', _this.handleViewportChangeEvents);
      if (wrapperNode) {
        wrapperNode.removeEventListener('scroll', _this.handleWrapperScroll);
        wrapperNode.removeEventListener('resize', _this.handleWrapperScroll);
      }
    };

    _this.loadOnVerticalScroll = function () {
      var distanceOfElementFromTop = _this.state.distanceOfElementFromTop;
      var thresholdY = _this.props.thresholdY;

      var scrollYDistance = (0, _utils.currentScrollPosition)().scrollY;
      var scrolledFromTop = window.innerHeight + scrollYDistance;
      return distanceOfElementFromTop - thresholdY < scrolledFromTop;
    };

    _this.loadOnHorizontalScroll = function () {
      var distanceOfElementFromLeft = _this.state.distanceOfElementFromLeft;
      var thresholdX = _this.props.thresholdX;

      var scrollXDistance = (0, _utils.currentScrollPosition)().scrollX;
      var scrolledFromLeft = window.innerWidth + scrollXDistance;
      return distanceOfElementFromLeft - thresholdX < scrolledFromLeft || distanceOfElementFromLeft < window.innerWidth;
    };

    _this.createObserver = function () {
      var _this$props2 = _this.props,
          thresholdX = _this$props2.thresholdX,
          thresholdY = _this$props2.thresholdY;

      var options = {
        root: null,
        rootMargin: '0px ' + thresholdX + 'px ' + thresholdY + 'px 0px',
        threshold: 0.0
      };

      _this.observer = new IntersectionObserver(_this.handleViewportChange, options);
      _this.observer.observe(_this.placeholderNode);
    };

    _this.handleViewportChange = function (changes) {
      var noLazyHorizontalScroll = _this.props.noLazyHorizontalScroll;

      changes.forEach(function (change) {
        if (noLazyHorizontalScroll) {
          if (change.intersectionRatio > 0) {
            _this.setState({ renderLazyLoadedComponent: true });
            _this.observer.disconnect();
          }
        } else {
          var scrollXDistance = (0, _utils.currentScrollPosition)().scrollX;
          var scrollYDistance = (0, _utils.currentScrollPosition)().scrollY;
          var scrolledFromTop = (0, _lodash4.default)(change, 'rootBounds.height', 0) + scrollYDistance;
          var scrolledFromLeft = (0, _lodash4.default)(change, 'rootBounds.width', 0) + scrollXDistance;
          var distanceOfElementFromTop = (0, _lodash4.default)(change, 'boundingClientRect.top', 0);
          var distanceOfElementFromLeft = (0, _lodash4.default)(change, 'boundingClientRect.left', 0);
          if (distanceOfElementFromTop < scrolledFromTop && distanceOfElementFromLeft < scrolledFromLeft) {
            _this.setState({ renderLazyLoadedComponent: true });
            _this.observer.disconnect();
          }
        }
      });
    };

    _this.callCallback = function () {
      var callback = _this.props.callback;
      var callbackCalled = _this.state.callbackCalled;

      if (!callbackCalled && typeof callback === 'function') {
        callback();
        _this.setState({ callbackCalled: true });
      }
    };

    _this.state = {
      renderLazyLoadedComponent: false,
      isIntersectionObserverAvailableinWindow: (0, _utils.isIntersectionObserverSupported)(),
      callbackCalled: false,
      distanceOfElementFromTop: undefined,
      distanceOfElementFromLeft: undefined
    };
    _this.observer = null;
    _this.placeholderNode = null;
    var throttleWait = _this.props.throttleWait;

    _this.handleViewportChange = _this.handleViewportChange.bind(_this);
    _this.handleWrapperScroll = _this.handleWrapperScroll.bind(_this);
    _this.handleWrapperScroll = (0, _lodash2.default)(_this.handleWrapperScroll, throttleWait);
    _this.addEventListeners = _this.addEventListeners.bind(_this);
    _this.removeEventListeners = _this.removeEventListeners.bind(_this);
    _this.handleViewportChangeEvents = _this.handleViewportChangeEvents.bind(_this);
    _this.handleViewportChangeEvents = (0, _lodash2.default)(_this.handleViewportChangeEvents, throttleWait);
    _this.horizontalEventAdded = false;
    _this.forcefulHorizontalScroll = false;
    return _this;
  }

  _createClass(ReactComponentLazyLoader, [{
    key: 'componentDidMount',
    value: function componentDidMount() {
      var isIntersectionObserverAvailableinWindow = this.state.isIntersectionObserverAvailableinWindow;

      this.placeholderNode = (0, _reactDom.findDOMNode)(this);
      if (_typeof(this.placeholderNode) === 'object') {
        this.setPlaceholderNodePosition();
        if (isIntersectionObserverAvailableinWindow) {
          this.createObserver();
        } else {
          this.addEventListeners();
        }
      }
    }
  }, {
    key: 'componentWillUnmount',
    value: function componentWillUnmount() {
      var isIntersectionObserverAvailableinWindow = this.state.isIntersectionObserverAvailableinWindow;

      if (isIntersectionObserverAvailableinWindow) {
        this.observer.disconnect();
      } else {
        window.removeEventListener('resize', this.handleViewportChangeEvents);
        window.removeEventListener('scroll', this.handleViewportChangeEvents);
      }
    }
  }, {
    key: 'render',
    value: function render() {
      var _props = this.props,
          children = _props.children,
          placeholder = _props.placeholder;
      var renderLazyLoadedComponent = this.state.renderLazyLoadedComponent;

      if (renderLazyLoadedComponent) {
        return React.createElement(
          React.Fragment,
          null,
          children,
          this.callCallback()
        );
      }
      return placeholder;
    }
  }]);

  return ReactComponentLazyLoader;
}(React.Component);

ReactComponentLazyLoader.defaultProps = {
  placeholder: React.createElement('div', null),
  thresholdX: 0,
  thresholdY: 0,
  wrapperID: null,
  callback: null,
  noLazyHorizontalScroll: false,
  throttleWait: 75
};
ReactComponentLazyLoader.propTypes = {
  callback: _propTypes.PropTypes.func,
  children: _propTypes.PropTypes.node.isRequired,
  noLazyHorizontalScroll: _propTypes.PropTypes.bool,
  placeholder: _propTypes.PropTypes.node,
  thresholdX: _propTypes.PropTypes.number,
  thresholdY: _propTypes.PropTypes.number,
  throttleWait: _propTypes.PropTypes.number,
  wrapperID: _propTypes.PropTypes.string
};
exports.default = ReactComponentLazyLoader;