How to get the values of the last 4 columns with Jquery

Question

I have a panelGrid, and would like to know how to get the last 4 elements before a given of the same line.

That is, I have a line, and the last element will receive the sum of the previous four.

Thank you

Answer 1

Using the jQuery selector together with the array function forEach you can select the last 5 elements of the set, add the first 4 and when you arrive at the last assign the total value of the sum.

Following example:

var total = 0;
Array.prototype.forEach.call($('.columnRight > label'), function(val, idx, arr) {
  if(arr.length > 5 ? idx > arr.length - 6 ? true : false : false) {
    if(idx == arr.length - 1) {
      val.textContent = total;
    } else {
      total = total + parseInt(val.textContent);
    }
  }
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="columnRight">
  <label>1</label>
  <label>2</label>
  <label>3</label>
  <label>4</label>
  <label>5</label>
  <label>6</label>
  <label></label>
</div>

In this line if(arr.length > 5 ? idx > arr.length - 6 ? true : false : false) { I used a ternary operation to avoid a nesting of if's, basically it checks whether the amount of elements in the array is greater than 5, if it checks whether the current index is greater than the amount of elements in the array minus six, if it does the rest of the operation. Learn more about ternary operations here.

The last label has the sum of the values of the 4 previous to it.

See working on jsfiddle.

Reference: MDN - foreach.