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How to sort array by date substring?

In a web app for which I'm responsible, I've been asked to sort contents of a form field by date descending using the date that starts each list item. I'd like to do this either onBlur or onSave because users are entering stuff willy-nilly. In any event, though I can very easily sort items alphabetically using javascript's array sort() method, sorting by date substring descending is whole 'nuther kettle of fish.

Here's an example of what I'd need to sort by date descending (and yes, each item has a bullet char):

•01/21/2013 - something happened; something else happened on 01/30/2013.
•04/02/2014 - John J. buys a new car
•02/25/2014 - We went to a movie. It was awesome, but a better one comes out on 12/31/2019.
•05/21/2012 - Let's keep sorting things.

Let's say the above is all included in a form field with id=myActivities. I'd like to, onBlur, get this:

•04/02/2014 - John J. buys a new car
•02/25/2014 - We went to a movie. It was awesome, but a better one comes out on 12/31/2019.
•01/21/2013 - something happened; something else happened on 01/30/2013.
•05/21/2012 - Let's keep sorting things.

Any brilliant sorters out there? I'm at your mercy.

By the way, in a windows app I can use to edit/update existing content, I use the (slightly proprietary looking) jscript code below. It works properly, but it's simple alphabetical sorting. Nothing to do with substring dates.

****************************************

var sortBox = new Array("Events");

function onRecordSave()
{
var i;
var es = Application.entrySeparator;
var fieldBox; // box object
var fieldString; // contents of the box
var entryArray; // array of field entries

// This loop will sort the entries in each box listed
// above, individually.
for (i = 0; i < sortBox.length; i++)
{
fieldBox = Form.boxes(sortBox[i]);
if (fieldBox) // ensure that the box exists
{
fieldString = fieldBox.content;
entryArray = fieldString.split(es);

// sort the entries using the JScript sort method
entryArray = entryArray.sort();
fieldString = entryArray.join(es);
fieldBox.content = fieldString;
}
}
}

gr8gonzo

My personal opinion is that you're not sorting correctly if you want to sort based on a substring. You CAN, but it would be highly unreliable.

My recommendation would be to parse the content into an array of objects, where each object has a date property (which holds a Date object that is built from the MM/DD/YYYY string value) and an event property (to hold the text part of each record/line).

Then simply sort on the date property, and Javascript will handle the detection of which date is greater than the other. Example:

<script>
// Start with one big block of unsorted text
var str = "•01/21/2013 - something happened; something else happened on 01/30/2013.\n" + 
"•08/17/2019 - Today\n" + 
"•04/02/2014 - John J. buys a new car\n" + 
"•02/25/2014 - We went to a movie. It was awesome, but a better one comes out on 12/31/2019.\n" + 
"•05/21/2012 - Let's keep sorting things. ";

// Parse into an array of objects
listOfEvents = [];
var matchResult;
var re = new RegExp("^.([0-9]{2}/[0-9]{2}/[0-9]{4}) - ([^•]+)", "gms"); // Regex to match an entry

// Keep looping through all matches
while(matchResult = re.exec(str))
{
  // Build a new object with a "date" and an "event" property
  listOfEvents.push({ date: new Date(matchResult[1]), event: matchResult[2] });
}

// Sort the array by the date property in descending order
listOfEvents.sort((a, b) => (a.date > b.date) ? -1 : 1) // -1 : 1 = Descending, 1 : -1 = Ascending

// Tada!
console.log(listOfEvents);
</script>

Open in new window

From there, you could loop through the sorted list and reconstruct it back as one big text block if you wanted to.

leakim971

function onRecordSave() {
    var es = Application.entrySeparator;
    var rgx =  /\d\d\/\d\d\/\d\d/;
    var myActivities = document.getElementById("myActivities").value.split(es);
    myActivities.sort(function(box1, box2) {
        var date1 = box1.match(rgx)[0];
        var date2 = box2.match(rgx)[0];
        return date2 - date1;
    });
    document.getElementById("myActivities").value = myActivities.join(es);
}