createBackup()

You can get backup

//It's an overloading method
adb.createBackup("backup_folder",(err,data) => {
    if(err) return console.log(err.message)
    console.log(data)//true
})

adb.createBackup((err,data) => {
    if(err) return console.log(err.message)
    console.log(data)//true
})