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In this case, your fileReader is outside of new Observable(() => ...), so the file my be load only once.

I think you have to create FileReader instance in new Observable(() => ...) so that every time you subscribe the observable object, a new FileReader instance will be created.

Simple sample code below:

This github issue seems to discuss issues around this error. Most commonly seems to be that the readFile function does not access local file system and it seems like you are trying to load from a local file system.

Here is a potential solution that I have used in the past to load an excel file then parse each sheet into json data. NOTE: this was in an angular 12 project but the same readExcel function can be used.

component.html code:

react-html-table-to-excel

Here, you need to create a html table and then that table gets converted to excel. I hid the table using CSS so that i only get the export excel button.

The example below shows this with a brand new workbook, with two sheets from two different tables:

1. text inside tr instead of td in dynamic content. This results in the table structure like below.

1. XLSX.utils.table_to_book called before table content created.

Working Demo

https://jsfiddle.net/aswinkumar863/95zsfg64/1/

You can transpose the sheet_to_json output to achieve this. Refer to this issue. Note sheet_to_json is called with {header: 1}:

1. XLSX.read expects you to pass the contents of the file (your comment even says so, it's supposed to be a node buffer with the data in it). You are passing a file name though, so it's handles as if you had a CSV file containing one cell with the file name in it. Look at your A1! It's not even the right content. You need XLSX.readFile instead!

2. You have a backslash in your path but you forgot to escape it (a backslash has a special meaning in a string literal). Add a second backslash in front.

So the fixed code is:

1. Transform the data by arranging the id and data properties from each object into a long list
2. Add an order property which is the number at the end of the id e.g. 1 for tagID1
3. Sort that new array by Timestamp then order - this may be unnecessary if your data is already in that order
4. Parse out the headers and create pairs of tagIDN quality and tagIDN value
5. Cast the data into a wide format by taking unique timestamps and creating 1 row per timestamp with as many column pairs as there are tags
6. Steps 4 and 5 are creating an array of arrays which can be passed to the XLSX method XLSX.utils.aoa_to_sheet
7. Because those long timestamps will be converted to scientific notation by Excel, set them to a number format of 0
8. Create a workbook, insert a sheet with the method from step 6 and save

Working code: