jexcel实现冻结行

在依赖中找到jexcel的源码，我们只需要关注scrollControls (滚动控制)，updateFreezePosition(更新冻结位置) 这两个方法：

 obj.scrollControls = function(e) {
            obj.wheelControls()

            if (obj.options.freezeColumns > 0 && obj.content.scrollLeft != scrollLeft) {
                obj.updateFreezePosition()
            }

            // Close editor
            if (obj.options.lazyLoading == true || obj.options.tableOverflow == true) {
                if (obj.edition && e.target.className.substr(0, 9) != 'jdropdown') {
                    obj.closeEditor(obj.edition[0], true)
                }
            }
        }

 obj.updateFreezePosition = function() {
            scrollLeft = obj.content.scrollLeft
            var width = 0
            if (scrollLeft > 50) {
                for (var i = 0; i < obj.options.freezeColumns; i++) {
                    if (i > 0) {
                        width += parseInt(obj.options.columns[i - 1].width)
                    }
                    obj.headers[i].classList.add('jexcel_freezed')
                    obj.headers[i].style.left = width + 'px'
                    for (var j = 0; j < obj.rows.length; j++) {
                        if (obj.rows[j] && obj.records[j][i]) {
                            var shifted = scrollLeft + (i > 0 ? obj.records[j][i - 1].style.width : 0) - 51 + 'px'
                            obj.records[j][i].classList.add('jexcel_freezed')
                            obj.records[j][i].style.left = shifted
                        }
                    }
                }
            } else {
                for (var i = 0; i < obj.options.freezeColumns; i++) {
                    obj.headers[i].classList.remove('jexcel_freezed')
                    obj.headers[i].style.left = ''
                    for (var j = 0; j < obj.rows.length; j++) {
                        if (obj.records[j][i]) {
                            obj.records[j][i].classList.remove('jexcel_freezed')
                            obj.records[j][i].style.left = ''
                        }
                    }
                }
            }

            // Place the corner in the correct place
            obj.updateCornerPosition()
        }

这里面有个bug，就是合并单元格列数大于冻结列数，拖动横向滚动条无限延伸，其实也很好理解，因为它源码写的就是将单元格加上冻结类名,固定左侧，如果冻结两列，而合并列有20列，拖动横向滚动条，合并的单元格就无限延伸了。我目前想到比较简单粗暴的方法是合并列的单元格不加冻结类名。

2.源码上加上冻结行的功能(clickReportItem是jexcel实例，因为我做的自定义报表，有多个jexcel表格，如果你只有一个jexcel表格，直接用你创建的实例替换就可以了)：

 clickReportItem.spread.scrollControls = function (e) {
                    clickReportItem.spread.wheelControls()
                    // 拖动滚动条距离超过冻结行列宽，高度
                    if (
                        (clickReportItem.freezeColumns > 0 && clickReportItem.spread.content.scrollLeft != scrollLeft) ||
                        (clickReportItem.freezeRows > 0 && clickReportItem.spread.content.scrollTop != scrollTop)
                    ) {
                        clickReportItem.spread.updateFreezePosition()
                    }

                    // Close editor
                    if (
                        clickReportItem.spread.options.lazyLoading == true ||
                        clickReportItem.spread.options.tableOverflow == true
                    ) {
                        if (clickReportItem.spread.edition && e.target.className.substr(0, 9) != 'jdropdown') {
                            clickReportItem.spread.closeEditor(clickReportItem.spread.edition[0], true)
                        }
                    }
                }

                var scrollTop = 0
                // 更新冻结位置
                clickReportItem.spread.updateFreezePosition = function () {
                    scrollTop = clickReportItem.spread.content.scrollTop
                    var width = 0
                    var height = 0
                    // 冻结行
                    if (scrollTop > 0) {
                        for (let i = 0; i < clickReportItem.freezeRows; i++) {
                            if (i > 0) {
                                height += parseInt(clickReportItem.spread.records[i - 1][0].style.height)
                            }
                            for (let j = 0; j < clickReportItem.spread.records[i].length; j++) {
                                if (clickReportItem.spread.rows[i] && clickReportItem.spread.records[i][j]) {
                                    let shifted = scrollTop - 1 + 'px'
                                    // 当前行下标(data-y:从0开始计算，加一)
                                    let rowIndex =
                                        (clickReportItem.spread.rows[i].getAttribute('data-y')
                                            ? Number(clickReportItem.spread.rows[i].getAttribute('data-y'))
                                            : 0) + 1
                                    let rowspan = clickReportItem.spread.records[i][j].getAttribute('rowspan')
                                        ? Number(clickReportItem.spread.records[i][j].getAttribute('rowspan'))
                                        : 0
                                    // 合并至第几行(rowspan包括当前行，减一)
                                    let mergeRowIndex = rowIndex + rowspan - 1
                                    if (
                                        !(
                                            clickReportItem.spread.records[i][j].getAttribute('data-merged') &&
                                            mergeRowIndex > clickReportItem.freezeRows
                                        )
                                    ) {
                                        clickReportItem.spread.records[i][j].classList.add('jexcel_freezed')
                                        clickReportItem.spread.records[i][j].style.top = shifted
                                    }
                                }
                            }
                        }
                    } else {
                        for (let i = 0; i < clickReportItem.freezeRows; i++) {
                            for (let j = 0; j < clickReportItem.spread.records[i].length; j++) {
                                if (clickReportItem.spread.rows[i] && clickReportItem.spread.records[i][j]) {
                                    // 合并单元格列数大于冻结列数，不加冻结类名，否则无限延伸
                                    clickReportItem.spread.records[i][j].classList.remove('jexcel_freezed')
                                    clickReportItem.spread.records[i][j].style.top = 0
                                }
                            }
                        }
                    }

                    // Place the corner in the correct place
                    clickReportItem.spread.updateCornerPosition()
                }