Node.js

Get a Header Attribute of a Related Item

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Demonstrates the Chilkat Email.GetRelatedAttr method, which returns a header-field attribute value from a header field of the Nth related item. The first argument is the zero-based related-item index, the second names a header field, and the third names an attribute within it. This example loads an image from a file into a BinData object, adds it as a related item with AddRelatedBd (capturing the generated Content-ID and referencing it from the HTML), then reads the name attribute of the related item's Content-Type header.

Background: Related items (inline images, style sheets) are MIME parts whose headers may carry named parameters — for instance Content-Type: image/png; name="logo.png". Because an image is binary, it is loaded into a BinData object (here from a file) and added with AddRelatedBd, rather than being treated as text. GetRelatedAttr then extracts one named attribute from a chosen header of a specific related part, the related-item analogue of GetAttachmentAttr, so you don't have to parse the raw header yourself.

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function chilkatExample() {

    var success = false;

    //  Demonstrates the GetRelatedAttr method, which returns a header-field attribute value
    //  from a header field of the Nth related item.  The first argument is the zero-based related-item
    //  index, the second is the header field name, and the third is the attribute name.

    var email = new chilkat.Email();
    email.Subject = "GetRelatedAttr example";

    //  Load the image data from a file into a BinData object.
    var bdImage = new chilkat.BinData();
    success = bdImage.LoadFile("qa_data/images/logo.png");
    if (success == false) {
        console.log(bdImage.LastErrorText);
        return true;
    }

    //  Add the image as a related item from the BinData; capture its generated Content-ID.
    var cid = email.AddRelatedBd("logo.png",bdImage);
    if (email.LastMethodSuccess == false) {
        console.log(email.LastErrorText);
        return true;
    }

    //  Reference the related item in the HTML body by its Content-ID.
    var sbHtml = new chilkat.StringBuilder();
    sbHtml.Append("<html><body><img src=\"cid:PLACEHOLDER_CID\"/></body></html>");
    var numReplaced = sbHtml.Replace("PLACEHOLDER_CID",cid);
    email.SetHtmlBody(sbHtml.GetAsString());

    //  Get the "name" attribute of the related item's Content-Type header (index 0).
    var val = email.GetRelatedAttr(0,"Content-Type","name");
    console.log("Related item Content-Type name attribute: " + val);

    //  Note: The path "qa_data/images/logo.png" is a relative local filesystem path,
    //  relative to the current working directory of the running application.

}

chilkatExample();