ahooks-v2/lib/useVirtualList/index.js

react hooks library

"use strict";

var __read = this && this.__read || function (o, n) {
  var m = typeof Symbol === "function" && o[Symbol.iterator];
  if (!m) return o;
  var i = m.call(o),
      r,
      ar = [],
      e;

  try {
    while ((n === void 0 || n-- > 0) && !(r = i.next()).done) {
      ar.push(r.value);
    }
  } catch (error) {
    e = {
      error: error
    };
  } finally {
    try {
      if (r && !r.done && (m = i["return"])) m.call(i);
    } finally {
      if (e) throw e.error;
    }
  }

  return ar;
};

var __importDefault = this && this.__importDefault || function (mod) {
  return mod && mod.__esModule ? mod : {
    "default": mod
  };
};

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

var react_1 = require("react");

var useSize_1 = __importDefault(require("../useSize"));

exports["default"] = function (list, options) {
  var containerRef = react_1.useRef();
  var size = useSize_1["default"](containerRef); // 暂时禁止 cache
  // const distanceCache = useRef<{ [key: number]: number }>({});

  var _a = __read(react_1.useState({
    start: 0,
    end: 10
  }), 2),
      state = _a[0],
      setState = _a[1];

  var itemHeight = options.itemHeight,
      _b = options.overscan,
      overscan = _b === void 0 ? 5 : _b;

  if (!itemHeight) {
    console.warn('please enter a valid itemHeight');
  }

  var getViewCapacity = function getViewCapacity(containerHeight) {
    if (typeof itemHeight === 'number') {
      return Math.ceil(containerHeight / itemHeight);
    }

    var _a = state.start,
        start = _a === void 0 ? 0 : _a;
    var sum = 0;
    var capacity = 0;

    for (var i = start; i < list.length; i++) {
      var height = itemHeight(i, list[i]);
      sum += height;

      if (sum >= containerHeight) {
        capacity = i;
        break;
      }
    }

    return capacity - start;
  };

  var getOffset = function getOffset(scrollTop) {
    if (typeof itemHeight === 'number') {
      return Math.floor(scrollTop / itemHeight) + 1;
    }

    var sum = 0;
    var offset = 0;

    for (var i = 0; i < list.length; i++) {
      var height = itemHeight(i, list[i]);
      sum += height;

      if (sum >= scrollTop) {
        offset = i;
        break;
      }
    }

    return offset + 1;
  };

  var calculateRange = function calculateRange() {
    var element = containerRef.current;

    if (element) {
      var offset = getOffset(element.scrollTop);
      var viewCapacity = getViewCapacity(element.clientHeight);
      var from = offset - overscan;
      var to = offset + viewCapacity + overscan;
      setState({
        start: from < 0 ? 0 : from,
        end: to > list.length ? list.length : to
      });
    }
  };

  react_1.useEffect(function () {
    calculateRange();
  }, [size.width, size.height, list.length]);
  var totalHeight = react_1.useMemo(function () {
    if (typeof itemHeight === 'number') {
      return list.length * itemHeight;
    }

    return list.reduce(function (sum, _, index) {
      return sum + itemHeight(index, list[index]);
    }, 0);
  }, [list.length]);

  var getDistanceTop = function getDistanceTop(index) {
    // 如果有缓存，优先返回缓存值
    // if (enableCache && distanceCache.current[index]) {
    //   return distanceCache.current[index];
    // }
    if (typeof itemHeight === 'number') {
      var height_1 = index * itemHeight; // if (enableCache) {
      //   distanceCache.current[index] = height;
      // }

      return height_1;
    }

    var height = list.slice(0, index).reduce(function (sum, _, i) {
      return sum + itemHeight(i, list[i]);
    }, 0); // if (enableCache) {
    //   distanceCache.current[index] = height;
    // }

    return height;
  };

  var scrollTo = function scrollTo(index) {
    if (containerRef.current) {
      containerRef.current.scrollTop = getDistanceTop(index);
      calculateRange();
    }
  };

  var offsetTop = react_1.useMemo(function () {
    return getDistanceTop(state.start);
  }, [state.start]);
  return {
    list: list.slice(state.start, state.end).map(function (ele, index) {
      return {
        data: ele,
        index: index + state.start
      };
    }),
    scrollTo: scrollTo,
    containerProps: {
      ref: function ref(ele) {
        containerRef.current = ele;
      },
      onScroll: function onScroll(e) {
        e.preventDefault();
        calculateRange();
      },
      style: {
        overflowY: 'auto'
      }
    },
    wrapperProps: {
      style: {
        width: '100%',
        height: totalHeight - offsetTop,
        marginTop: offsetTop
      }
    }
  };
};