var request = { 
"type" : "readAttachment",
"data" : {
        "Id" : "001234567891234",    // Required attachment Id
        "ReturnBase64Data" : false   // Optional, default true.  If false you will still have access to URL of attachment
    }
};
bridge.sendRequest(request, function (responseData) { alert('The Attachment is located here: ' + responseData.data[0].FileURL });

Normal data reads through 'select' API will not contain Base64 Attachment data in the body field unless that body field has previously been queried from Salesforce or otherwise populated with Base64 data.

var request = {

"type" : "queryAttachment",
"data" : {
        "filter" : "ParentId = '001234567891234'"  
    

}
};
bridge.sendRequest(request, function (responseData) { alert('The first Attachment is located here: ' + responseData.data[0].FileURL });

The queryAttachment API call will NOT return the Attachment's Base64 Body field or the Base64 data representing the thumbnail.

The createAttachment method allows creation of Attachments directly from Base64 encoded data. The intended Attachment ParentId, Name, and Body are required arguments. The ContentType of the Attachment may be optionally specified in MIME type format, as in the example below. On success, the response data contains the Id of the created attachment.

var request = { 
"type" : "createAttachment",
"data" : { 
		"ParentId" : "001234567891234",             // Required
		"Name" : "AttachmentName.jpg",              // Required
		"Body" : "AABBCCDDEEFF...", // Base64 data --   Required
		"ContentType" : "image/jpeg" // Optional -- manual entry of content type
	} 
};
bridge.sendRequest(request, function (responseData) {
	if (responseData.type == "createAttachmentResponse") {
	 	alert('Created Attachment Id: ' + responseData.data); 
	}
	else {
		// error code
	}
});

var request = { 
"type" : "createAttachmentFromFilePath",
"data" : { 
		"ParentId" : "001234567891234",            // Required
		"Name" : "AttachmentName.jpg",             // Optional
		"ContentType" : "image/jpeg",               // Optional -- manual entry of content type
		"FilePath" : "/Valid/Path/To/File.Jpg"     // Required
	} 
};
bridge.sendRequest(request, function (responseData) {
	if (responseData.type == "createAttachmentResponse") {
	 	alert('Created Attachment Id: ' + responseData.data); 
	}
	else {
		// error code
	}
});

The createAttachmentFromCamera method allows creation of Attachments directly from the device's camera. The intended Attachment ParentId is a required argument. Optionally, you can specify a file name for the attachment, instead of using the name of the original file. On success, the response data contains the Id of the created attachment.

var request = {

"type" : "createAttachmentFromCamera",
"data" : {
        

"ParentId" : "001234567891234",            // Required

        "Name" : "AttachmentName.jpg"             // Optional
    

}

};
bridge.sendRequest(request, function (responseData) {
 

   if (responseData.type == "createAttachmentResponse") {

        alert('Created Attachment Id: ' + responseData.data);
   

 }
  

  else {

        // error code
 

   }
});