ews-javascript-api getAttachments throw Object doesn't support this action

Question

I'm using ews-js-api-browser to develop an outlook desktop add-in.
EwsJS namespace is currently imported with a <script> tag, like office-js library.

Office.initialize = function (reason) {
    EwsJS.ConfigureForOutlook()
    EwsJS.EwsLogging.DebugLogEnabled = false
}

const functionWhichNeedAttachment = () => {
Office.context.mailbox.getCallbackTokenAsync((token) => {
    const exch = new EwsJS.ExchangeService(EwsJS.ExchangeVersion.Exchange2016)
    exch.Credentials = new EwsJS.OAuthCredentials(token.value)
    exch.Url = new EwsJS.Uri(Office.context.mailbox.ewsUrl)

    exch.GetAttachments(
      [Office.context.mailbox.item.attachments[0].id],
      1,
      null).then(res => console.log('res', res))

  })
})
}

I get this error :

Object doesn't support this action ExchangeWebService.js (41867, 9)

It seems like ExchangeWebService is trying to assign a value to a forbidden keyword.

Answer 1

Please take a look at https://learn.microsoft.com/en-us/outlook/add-ins/web-services

there is only subset of EWS operations available using mailbox.makeEwsRequestAsync which is internally used by ews-javascript-api for Outlook/Mail app.

unfortunately GetAttachments is not available in mail apps.