Javascript-Google App Script. I'm getting TypeError: Cannot read property 'map' of undefined

Question

I have this code in Google Docs, I'm trying to create a registry sheet with data from the other sheets, but I keep getting TypeError: Cannot read property 'map' of undefined. What could be the problem?

function processData(sheetData){

 var transpose = m => m[0].map((x,i) => m.map(x => x[i]))
 
 var data = sheetData.map(x=>x.slice(0,lastRow))
 
 data[1] = data[1].map((l => (v, i) => l = v === ''  ? l : v)());
 var transposedData = transpose(data)
 transposedData[0] = transposedData[0].map((l => (v, i) => l = v === ''  ? l : v)());
 data = transpose(transposedData)
 
 var dataFilterProjects = data.filter(row=> row.slice(2,).map(j=> (j!='') ? 1 : 0).reduce((a, b) => a + b, 0)!=0)
 var dataFilterDays = transpose(transpose(dataFilterProjects).filter(row=> row.slice(4,).map(j=> (j!='') ? 1 : 0).reduce((a, b) => a + b, 0)!=0))
 var dataTotalFilter = dataFilterDays.filter(row=> row[1]!= 'Total')
 
 return dataTotalFilter
}