@nutui/nutui-react
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京东风格的轻量级移动端 React 组件库，支持一套代码生成 H5 和小程序
115 lines (114 loc) • 4.56 kB
JavaScript
// 缓存列表初始化信息
var initPositinoCache = function(reaItemSize) {
var length = arguments.length > 1 && arguments[1] !== void 0 ? arguments[1] : 0;
var index = 0;
var positions = Array(length);
while(index < length){
positions[index] = {
index: index,
height: reaItemSize,
width: reaItemSize,
top: index * reaItemSize,
bottom: (index + 1) * reaItemSize,
left: index * reaItemSize,
right: (index + 1) * reaItemSize
};
index++;
}
return positions;
};
// 获取列表总高度
var getListTotalSize = function(positions, horizontal) {
var index = positions.length - 1;
var size = 0;
if (index < 0) {
size = 0;
} else {
size = horizontal ? positions[index].right : positions[index].bottom;
}
return size;
};
// 通过二分法找到 scrollOffset 对应的值
var binarySearch = function(positionsList, horizontal) {
var value = arguments.length > 2 && arguments[2] !== void 0 ? arguments[2] : 0;
var start = 0;
var end = positionsList.length - 1;
var tempIndex = null;
var key = horizontal ? 'right' : 'bottom';
while(start <= end){
var midIndex = Math.floor((start + end) / 2);
var midValue = positionsList[midIndex][key];
// 相等则直接返回（因为是bottom, 因此startIndex应该是下一个节点）
if (midValue === value) {
return midIndex + 1;
}
// 中间值 < 传入值，则说明 value对应的节点 大于 start, start往后移动一位
if (midValue < value) {
start = midIndex + 1;
} else if (midValue > value) {
// tempIndex存放最靠近值为value的所有
if (tempIndex === null || tempIndex > midIndex) {
tempIndex = midIndex;
}
end = midIndex - 1;
}
}
tempIndex = tempIndex || 0;
return tempIndex;
};
var getEndIndex = function(param) {
var list = param.list, startIndex = param.startIndex, visibleCount = param.visibleCount, _param_itemEqual = param.itemEqual, itemEqual = _param_itemEqual === void 0 ? true : _param_itemEqual, positions = param.positions, offSetSize = param.offSetSize, overscan = param.overscan, _param_sizeKey = param.sizeKey, sizeKey = _param_sizeKey === void 0 ? 'width' : _param_sizeKey;
var dataLength = list.length;
var tempIndex = null;
if (itemEqual) {
var endIndex = startIndex + visibleCount;
tempIndex = dataLength > 0 ? Math.min(dataLength, endIndex) : endIndex;
} else {
var sizeNum = 0;
for(var i = startIndex; i < dataLength; i++){
sizeNum += positions[i][sizeKey] || 0;
if (sizeNum > offSetSize) {
var endIndex1 = i + overscan;
tempIndex = dataLength > 0 ? Math.min(dataLength, endIndex1) : endIndex1;
break;
}
}
if (sizeNum < offSetSize) {
tempIndex = dataLength;
}
}
tempIndex = tempIndex || 0;
return tempIndex;
};
// 更新Item大小
var updateItemSize = function(positions, items, sizeKey, margin) {
var newPos = positions.concat();
Array.from(items).forEach(function(item) {
var index = Number(item.getAttribute('data-index'));
var styleVal = item.getAttribute('style');
if (styleVal && styleVal.includes('none')) return;
var nowSize = item.getBoundingClientRect()[sizeKey];
if (margin) nowSize += margin;
var oldSize = positions[index][sizeKey];
// 存在差值, 更新该节点以后所有的节点
var dValue = oldSize - nowSize;
if (dValue) {
if (sizeKey === 'width') {
newPos[index].right -= dValue;
newPos[index][sizeKey] = nowSize;
for(var k = index + 1; k < positions.length; k++){
newPos[k].left = positions[k - 1].right;
newPos[k].right -= dValue;
}
} else if (sizeKey === 'height') {
newPos[index].bottom -= dValue;
newPos[index][sizeKey] = nowSize;
for(var k1 = index + 1; k1 < positions.length; k1++){
newPos[k1].top = positions[k1 - 1].bottom;
newPos[k1].bottom -= dValue;
}
}
}
});
};
export { initPositinoCache, getListTotalSize, binarySearch, getEndIndex, updateItemSize, };