I’m making use of javascript to read the excel file with exceljs but I see that the javascript function is returning the response to my html event listerner and continuining execution and reading the content of file.
How can i make this code to return value after all lines of code are executed completely. Please help as I’m new to Javascript and have built this code by loooking at lot of online resources
readAndProcess(files) {
return new Promise(resolve => {
try {
const file = files[0];
let fileContent = [];
const fileReader = new FileReader();
fileReader.readAsArrayBuffer(file);
fileReader.onload = (e) => {
let result = e.target.result;
let columns = [];
let tableData = [];
let size;
if (result) {
// Create workbook & add worksheet
const wb = new ExcelJS.Workbook();
wb.xlsx.load(result).then(workbook => {
console.log(workbook, 'workbook instance');
workbook.eachSheet((sheet, id) => {
sheet.eachRow((row, rowIndex) => {
console.log(rowIndex, 'rowIndex');
console.log(row);
if (rowIndex === 1) {
columns = Object.entries(row.values).map(([k, v]) =>
({
field: v,
headerText: v
})
);
} else {
const part = {};
let index = 0;
Object.entries(row.values).map(([k, v]) => {
part[columns[index].field] = v;
index++;
}
);
tableData.push(part);
//console.log(tableData);
};
});
});
});
resolve({
success: true,
result: {
name: file.name,
size: file.size,
type: file.type,
columns: columns,
tableData: tableData
},
error: {
detail: ''
}
});
} else {
resolve({
success: false,
error: {
detail: 'Empty File : ' + result
}
})
}
}
} catch (err) {
resolve({
success: false,
error: {
detail: 'Error while reading file : ' + err.detail
}
});
}
});
}
}