User friendly page rotation about mupdf.js HOT 5 OPEN

const fs = require("fs")
const mupdf = require("mupdf")

var doc = mupdf.Document.openDocument(fs.readFileSync("input.pdf"), "application/pdf")
var page = doc.loadPage(0)

// Get the PDF object corresponding to the page
var page_obj = page.getObject()

// Look up the existing page rotation (inheritable from the page tree, see PDF reference for details)
var rotate = page_obj.getInheritable("Rotate")
if (!rotate)
    rotate = 0

// Update the Rotate value
page_obj.put("Rotate", rotate + 90)

// Save the changes to a new file.
fs.writeFileSync("output.pdf", doc.saveToBuffer("incremental").asUint8Array())

// Look up the existing page rotation (inheritable from the page tree, see PDF reference for details)
    let rotate = page_obj.getInheritable("Rotate")
    console.log("rotate="+rotate) // rotate=11845304
    if (!rotate)
        rotate = 0

    // Update the Rotate value
    page_obj.put("Rotate", rotate + 90)