Angular how to read an excel file from an assets folder using typeScript

Question

Ashamed to ask, but for resolving my problem I need to ask. So, I have a problem with reading data from an excel file in my Angular project. The file is located in the assets folder.

I know how to get a file from the folder.

In app.component.ts inside ngOnInit I get a file:

ngOnInit() {
  this.http.get('assets/dataTest.xlsx').subscribe((data: any) => {
    console.log("get: " + data);
  });
}

How I understand inside http.get I need to use code below:

const reader: FileReader = new FileReader();
reader.onload = (e: any) => {
  console.log("READ " + e);
};
reader.readAsBinaryString(data);

But it does not work. I get an error:

ERROR TypeError: Failed to execute 'readAsBinaryString' on 'FileReader': parameter 1 is not of type 'Blob'.

Help me please with reading data from an excel file is located in the assets folder.

Answer 1

I suggest to use a library to parse the excel file.

See there an example of SheetJs :

/* <input type="file" (change)="onFileChange($event)" multiple="false" /> */
/* ... (within the component class definition) ... */
  onFileChange(evt: any) {
    /* wire up file reader */
    const target: DataTransfer = <DataTransfer>(evt.target);
    if (target.files.length !== 1) throw new Error('Cannot use multiple files');
    const reader: FileReader = new FileReader();
    reader.onload = (e: any) => {
      /* read workbook */
      const bstr: string = e.target.result;
      const wb: XLSX.WorkBook = XLSX.read(bstr, {type: 'binary'});

      /* grab first sheet */
      const wsname: string = wb.SheetNames[0];
      const ws: XLSX.WorkSheet = wb.Sheets[wsname];

      /* save data */
      this.data = <AOA>(XLSX.utils.sheet_to_json(ws, {header: 1}));
    };
    reader.readAsBinaryString(target.files[0]);
  }

Answer 2

i just solve the problem with this.

read() {
this.httpClient.get('assets/files/Report DTP.xls', { responseType: 'blob' })
  .subscribe((data: any) => {
    const reader: FileReader = new FileReader();

    let dataJson1;
    let dataJson2;

    reader.onload = (e: any) => {
      const bstr: string = e.target.result;
      const wb: XLSX.WorkBook = XLSX.read(bstr, { type: 'binary' });

      /* grab first sheet */
      const wsname1: string = wb.SheetNames[1];
      const ws1: XLSX.WorkSheet = wb.Sheets[wsname1];

      /* grab second sheet */
      const wsname2: string = wb.SheetNames[2];
      const ws2: XLSX.WorkSheet = wb.Sheets[wsname2];

      /* save data */
      dataJson1 = XLSX.utils.sheet_to_json(ws1);
      dataJson2 = XLSX.utils.sheet_to_json(ws2);
      console.log(dataJson1);

    };
    reader.readAsBinaryString(data);
    console.log(data);
  });

}

I hope it helps you even though it's late :)