multipart/formData Request in Node js

I am noobie in multipart/formdata request in node js.

I am crawling a website which does multipart/formdata request.This is how it does :

url : https://example.com
Content-Type: multipart/form-data;boundary=----

formdata : 
    Content-Disposition: form-data; name=field1
    value1

    Content-Disposition: form-data; name=field1
    value1

    Content-Disposition: form-data; name=field2
    value2

    Content-Disposition: form-data; name=field3
    value3

    Content-Disposition: form-data; name=field4
    value4

    Content-Disposition: form-data; name=^\^"theFile^\^"; filename=^\^"^\^"^
    Content-Type: application/octet-stream^

I am using request module of node js for doing that. This is how

 var options = { 
               method: 'POST',
               url: "https://example.com",
               formData : {
                           "field1" : "value1",
                           "field2" : "value2",
                           "field3" : "value3",
                           "field4" : "value4",
                           "theFile": {
                               "value":  "",
                               "options": {
                                    "filename": '',
                                    "contentType": 'application/octet-stream'
                               }
                          }
               }
}

Where i am doing wrong ?