@researchgate/react-intersection-list/lib/es/Sentinel.js

React List Component using the Intersection Observer API

function _createSuper(Derived) { var hasNativeReflectConstruct = _isNativeReflectConstruct(); return function _createSuperInternal() { var Super = _getPrototypeOf(Derived), result; if (hasNativeReflectConstruct) { var NewTarget = _getPrototypeOf(this).constructor; result = Reflect.construct(Super, arguments, NewTarget); } else { result = Super.apply(this, arguments); } return _possibleConstructorReturn(this, result); }; }

function _possibleConstructorReturn(self, call) { if (call && (typeof call === "object" || typeof call === "function")) { return call; } return _assertThisInitialized(self); }

function _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }

function _isNativeReflectConstruct() { if (typeof Reflect === "undefined" || !Reflect.construct) return false; if (Reflect.construct.sham) return false; if (typeof Proxy === "function") return true; try { Date.prototype.toString.call(Reflect.construct(Date, [], function () {})); return true; } catch (e) { return false; } }

function _getPrototypeOf(o) { _getPrototypeOf = Object.setPrototypeOf ? Object.getPrototypeOf : function _getPrototypeOf(o) { return o.__proto__ || Object.getPrototypeOf(o); }; return _getPrototypeOf(o); }

function _inheritsLoose(subClass, superClass) { subClass.prototype = Object.create(superClass.prototype); subClass.prototype.constructor = subClass; subClass.__proto__ = superClass; }

function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }

import React, { Component } from 'react';
import Observer from '@researchgate/react-intersection-observer';
import PropTypes from 'prop-types';
import { computeRootMargin } from './utils';

var Sentinel = /*#__PURE__*/function (_Component) {
  _inheritsLoose(Sentinel, _Component);

  var _super = _createSuper(Sentinel);

  function Sentinel(props) {
    var _this;

    _this = _Component.call(this, props) || this;

    _defineProperty(_assertThisInitialized(_this), "setRootElement", function (rootElement) {
      _this.setState({
        rootElement: rootElement
      });
    });

    _this.state = {
      rootElement: undefined,
      rootMargin: computeRootMargin(props)
    };
    _this.target = /*#__PURE__*/React.createElement("template", {
      style: {
        height: 1,
        minWidth: 1,
        display: 'block'
      }
    });
    props.setRef(_this.setRootElement);
    return _this;
  }

  Sentinel.getDerivedStateFromProps = function getDerivedStateFromProps(_ref, prevState) {
    var threshold = _ref.threshold,
        axis = _ref.axis;
    var newState = null;

    if (threshold !== prevState.threshold || axis !== prevState.axis) {
      newState = {
        threshold: threshold,
        axis: axis,
        rootMargin: computeRootMargin({
          threshold: threshold,
          axis: axis
        })
      };
    }

    return newState;
  };

  var _proto = Sentinel.prototype;

  _proto.shouldComponentUpdate = function shouldComponentUpdate(nextProps, _ref2) {
    var rootMargin = _ref2.rootMargin,
        rootElement = _ref2.rootElement;
    var _this$state = this.state,
        currentRootMargin = _this$state.rootMargin,
        currentRootElement = _this$state.rootElement; // When the rootMargin stays the same but the sentinel is repositioned, it can fall within
    // its threshold prematurely. In this case we don't get any update from the Observer instance.
    // We need to guarantee an update, and re-observing is a cheap way to accomplish this.

    if (currentRootMargin === rootMargin && currentRootElement === rootElement) {
      this.observer.externalUnobserve();
      this.observer.observe();
      return false;
    }

    return true;
  };

  _proto.render = function render() {
    var _this2 = this;

    var onChange = this.props.onChange;
    var _this$state2 = this.state,
        rootElement = _this$state2.rootElement,
        rootMargin = _this$state2.rootMargin;
    return /*#__PURE__*/React.createElement(Observer, {
      ref: function ref(instance) {
        _this2.observer = instance;
      },
      disabled: typeof rootElement === 'undefined',
      root: rootElement,
      rootMargin: rootMargin,
      onChange: onChange
    }, this.target);
  };

  return Sentinel;
}(Component);

process.env.NODE_ENV !== "production" ? Sentinel.propTypes = {
  axis: PropTypes.oneOf(['x', 'y']).isRequired,
  threshold: PropTypes.string.isRequired,
  setRef: PropTypes.func.isRequired,
  onChange: PropTypes.func.isRequired
} : void 0;
export default Sentinel;