FormData

Overview

This is a Google Apps Script library which enhances Class FormData to create a multipart/form-data.

Functions

Function	Description
newFormData()	This method return a new FormData's instance

FormData class

Methods	Description
append(name, value)	Adds a new field with the given name and value to the form data. If the value is a Blob object, the field is treated as a file and its content type is set accordingly.
getBoundary()	Returns the boundary string. the boudary are initialize with Date.now().toString(16)
getPayload()	Returns the payload format for send in multipart/form-data request

Library ID

You can add FormData in your script GAS with the following id: 1prPsBOOqOjDT5L_RFyv7MQp7pz1e1KU2c9UN8aoqzvvHqZSavuUFjeOc

Example

const formData = FormData.newFormData();
const file = DriveApp.getFileById("<YOUR_FILE_ID>")

formData.append("file", file)
formData.append("language", "en")

const payload = formData.getPayload();

const headers = {
    "Content-Type": `multipart/form-data; boundary=${formData.getBoundary()}`

// Now you can make a call
}