javascript maps make my head spin. 
Here is the solution at which I arrived:
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Create a meta-data Collection which lists each table/collection that should be user-downloadable along with the associated WIX codename associated to each column/field in those collections and the order in which you want those columns/fields to appear in a download.
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Use the following javascript and HTML code to query and order your data in the proper columnar order. (I left in all the console.log messages I used to develop this but they are all commented out. You can restore them as necessary to understand what is happening after creating your meta-data table and changing the collection names to reflect your collections).
Your meta-data collection table should be structured something like this:
The most import elements of that meta-data table are the CollectionCode and the FieldCode --which are how WIX Javascript identifies those elements programmatically.
here are the control elements on the website page which access the code:
They look like this in preview mode: (I set the HTML element to “hidden”)
//
here is the javascript code from the web page:
//
import wixData from ‘wix-data’ ;
$w . onReady ( function () {
$w ( “#html2” ). onMessage (( event ) => {
console . log ( “event data” , event . data )
$w ( “#text1” ). text = event . data ; // Write messages from html component to text1.
});
});
function sendMessageToComponent ( message ) {
// send message to the HTML element
console . log ( message )
$w ( “#html2” ). postMessage ( message );
}
export async function csvDownload () {
let collectionName = $w ( “#dropdown1” ). value //this dropdown list is data-connected to a meta-data collection which lists all the “end-user download-available” collections on the site
//console.log(collectionName)
let headerOrder = //initialize an array to hold the specific collection column order desired
await wixData . query ( “CollectionsMetaData” ) // this collection contains the collection and field names–and the field names are manually pre-assigned a numberic position value within the collection
. limit ( 1000 ) //I have 7 user-survey data input collections with over cumulative 400 fields so far
. eq ( ‘collectionCode’ , collectionName ) //look for the portion of meta data that applies to the selected collection from the dropdown list
. eq ( ‘includeInReport’ , “Yes” ) //get only the fields marked for inclusion in a download report
. ascending ( ‘position’ ) //MOST IMPORT–order the columnar items as indicated by the meta data position assignment!
. find ()
. then (( headers ) => {
for ( let x = 0 ; x < headers . length ; x ++) { //create an ordered array of “item” identifiers
//console.log(x,headers.items.fieldCode,headers.items.position)
headerOrder . push ([ headers . items [ x ]. fieldCode , headers . items [ x ]. position ]) //we add the fiedl WIX codenames to the array in the order we want them returned in the CSV file
}
//console.log(headerOrder)
})
. then ( async ( nextUp ) => { //now we will query the collection selected in the dorp-down list
await wixData . query ( collectionName )
. limit ( 1000 )
. find ()
. then ( async ( results ) => {
let jsonArr = “” //initialize a json array to be passed to the HTML element embedded in the page which contains the download code
if ( results . items . length > 0 ) { //make sure we have something to process
let tempArr = “” //initialize a temporary array to holed the queried values for one row at a time as they come in
for ( let r = 0 ; r < results . items . length ; r ++) { //determine how many records were detected in the collection
for ( let h = 0 ; h < headerOrder . length ; h ++) { //now determine which field we want to pass to JSON nesxt based on the preveiously queried meta data
let fieldcode = ( headerOrder [ h ][ 0 ]) //this is the WiX collection “codeNaeme” for the desired field
let qCode = “results.items[r].” + fieldcode ; //create a dynamic variable that refences the desired collection column for the results returned from the query collection
//console.log (qCode)
let fieldVal = eval( qCode ) //THIS IS THE SHIZNIT: we dynamically evaluate the value of the field/column we need IN THE PROPER (assigned) COLUMN ORDER
//tempArr.push([ fieldcode, fieldVal ])
let comma = “” ; //now we’re going to emulate what the JSON stringify command does to create a string we can pass to the HTML download code (courtesy of Steve Cropper)
if ( h < headerOrder . length - 1 ) { comma = ‘,’ } else { comma = ‘’ } //if this is our very last column, we don’t need a comma between elements, otherwise we do
tempArr += ‘"’ + fieldcode + ‘": "’ + fieldVal + ‘"’ + comma //format our data lin with the field title, the value, and (if necessaryy) a comma
}
let comma = “” ; //some final JSON stringify formatting (next 3 lines)
if ( r < results . length - 1 ) { comma = ‘,’ } else { comma = ‘’ }
tempArr = “{” + tempArr + “}” + comma //this separates each record detected by the primarily-targeted table collection query
//console.log(tempArr)
jsonArr += tempArr //add this row’s data line to our final jason array we will pass to the HTML code
tempArr = “” //reset the temp array to receive the next row’s data
}
} else { console . log ( “no results found” ) }
//console.log(jsonArr)
//let jsonPayload = JSON.stringify(jsonArr); //we don’t need this anymore–we’ve already created a “stringified” json array
let jsonPayload = “[” + jsonArr . replaceAll ( ‘\n\n’ , ‘\n\n’ ) + “]” //in my case, I had to do some clean-up to eliminate “escaped” new-linecharacters contained in collection text fields
//console.log("headers ",jsonPayload);
sendMessageToComponent ({ name : collectionName + “.csv” , action : “data” , payload : jsonPayload }); //finally, we send the results to Steve Cropper’s HTML code with one additionals value, i.e. “naem: collectionName”) which adds that name to the CSV download
});
});
}
export function button1_click ( event ) {
csvDownload ()
}
//
NOTES REGARDING THE HTML MESSAGE SECTION:
//
In order to pass a specific download filename:
this modification to the page javascript: " sendMessageToComponent ({ name : collectionName
requires a modification to Steve Cropper’s HTML Element code as follows:
function messageReceived(message) {
if (message && message.action === 'data' && message.payload) {
// Convert JSON to csv
download_file( **message.name** , csvFromJson(message.payload));
//
Here is the full HTML code pasted into the HTML page element:
//
Document Loading...
document.onreadystatechange = function () {
if (document.readyState === "complete") {
console.log("Document Loaded!");
updateNoticeBoard("Document Loaded!");
}
}
function updateNoticeBoard(message) {
let messageArea = document.getElementById('noticeBoard');
messageArea.innerHTML = message;
}
window.onmessage = (event) => {
console.log("Message Received: "+(event.data.action ? event.data.action : "Bad Message"));
if (event.data) {
messageReceived(event.data);
}
};
function sendMessageToPage(message) {
window.parent.postMessage(message, "*");
}
function messageReceived(message) {
if (message && message.action === 'data' && message.payload) {
// Convert JSON to csv
download_file(message.name, csvFromJson(message.payload));
} else if (message && message.payload) {
updateNoticeBoard(message.payload);
}
}
function dynamic_text() {
return "create your dynamic text here";
}
// Courtesy https://stackoverflow.com/questions/18249290/generate-csv-for-excel-via-javascript-with-unicode-characters
function download_file(name, contents, mime_type) {
mime_type = mime_type || "text/csv;charset=utf-8";
var blob = new Blob(['\uFEFF', contents], {type: mime_type});
var dlink = document.createElement('a');
dlink.download = name;
dlink.href = window.URL.createObjectURL(blob);
dlink.onclick = function(e) {
// revokeObjectURL needs a delay to work properly
var that = this;
setTimeout(function() {
window.URL.revokeObjectURL(that.href);
}, 1500);
};
dlink.click();
dlink.remove();
}
function csvFromJson(jsonData) {
const items = JSON.parse(jsonData);
const replacer = (key, value) => value === null ? '' : value // specify how you want to handle null values here
const header = Object.keys(items[0])
console.log(header)
let csv = items.map(row => header.map(fieldName => JSON.stringify(row[fieldName], replacer)).join(','))
csv.unshift(header.join(','))
csv = csv.join('\r\n')
console.log(csv)
return csv
}
</script>
Hope this may be of some use to anybody else facing the same issues.
As “Gramps” says: No cats were harmed in the development of this code"
In fact, they typically walk all over my keyboard while I’m trying to concentrate, therefore, I refuse to be held responsible for any grammatic, programmatic or logical errors.