Custom sort comparator for javascript string

Question

I have a custom comparator for sorting some strings which doesnt work as expected for sorting strings in descending order.

var list = document.getElementById('mylist');

var items = list.childNodes;
var itemsArr = [];
for (var i in items) {
  if (items[i].nodeType == 1) { // get rid of the whitespace text nodes
    itemsArr.push(items[i]);
  }
}
var sortOrder = "DESC";

itemsArr.sort(function(a, b) {
  switch (sortOrder) {
    case "ASC":
      var val = a.innerHTML.localeCompare(b.innerHTML);
      break;
    case "DESC":
      var val = a.innerHTML.localeCompare(b.innerHTML);
      if (val === 1)
        val = -1;
      if (val === -1)
        val = 1;
      break;

  }
  return val
});

/*itemsArr.sort(function(a, b) {
  return a.innerHTML == b.innerHTML
          ? 0
          : (a.innerHTML > b.innerHTML ? 1 : -1);
});*/

for (i = 0; i < itemsArr.length; ++i) {
  list.appendChild(itemsArr[i]);
}

<ul id="mylist">
  <li id="list-item3">Service</li>
  <li id="list-item4">Vendor</li>
  <li id="list-item2">Service_Type</li>
  <li id="list-item1">Call_Date</li>
  <li id="list-item3">Customer Sat Rating</li>
  <li id="list-item4">TTA</li>
  <li id="list-item2">Support_Rep</li>
  <li id="list-item1">Source_State</li>
  <li id="list-item3">Severity</li>
  <li id="list-item4">Customer_Type</li>
  <li id="list-item2">CALL ID</li>
  <li id="list-item1">Resolved_Ontime</li>
  <li id="list-item2">Product</li>
  <li id="list-item1">Minutes_On_Phone</li>
</ul>

For a different data I sorted earlier it worked fine for both ascending and descending. For the current html data it doesnt. Can someone please show where I am incorrect?

You should not have duplicate id's, they mess up the lookup table for the DOM. — Travis J
– Travis J, Commented Oct 5, 2015 at 21:57
To do descending sort with .localeCompare() you just need to use the unary - operator: val = -val; — Pointy
– Pointy, Commented Oct 5, 2015 at 21:59
In my working code, I do not have duplicate ID's. This html snippet is for stackoverflow. Still Ill edit it — phantomsays
– phantomsays, Commented Oct 5, 2015 at 21:59
@Pointy: Any small snippet you can point me to, that would be great. — phantomsays
– phantomsays, Commented Oct 5, 2015 at 22:01

Malk · Accepted Answer · 2015-10-05 22:03:10Z

2

You are setting it to DESC and then right back again:

case "DESC":
  var val = a.innerHTML.localeCompare(b.innerHTML);
  if (val === 1)
    val = -1;
  if (val === -1)
    val = 1;
  break;

Change it to:

case "DESC":
  var val = -1 * a.innerHTML.localeCompare(b.innerHTML);
  break;

answered Oct 5, 2015 at 22:03

Malk

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1 Comment

Pointy Over a year ago

You don't need the * operator. Just apply the - unary operator to the return value: -a.innerHTML.localeCompare(b.innerHTML)

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