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()
}
