`json_to_sheet` mutates header array

While I try to change header titles by passing array of titles to options like below it does not override the headers. Instead it writes new headers first and original data with old headers again from next cell.

I am experiencing the same problem.

In addition, sheets js is mutating the header array passed in, which is not something I would ever expect.

Example:

const header = ['field2', 'field3'];
const data = [{field1: 'foo', 'field2': 'bar', 'field3': 'baz'}]

const worksheet = XLSX.utils.json_to_sheet(data, {header});

console.log(header); // RESULTS:  ["field2", "field3", "field1"]

_Originally posted by @paustint in https://github.com/SheetJS/sheetjs/issues/1487#issuecomment-706759470_

[SheetJSDev]

Now that you understand this, maybe you can help improve the docs 😃 We’ll accept a PR that clarifies the behavior.

[reviewher]

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