return specific index of array using val() in jquery

I may lack basic knowledge of retrieving data in Javascript. So I am reading the value of range slider using a jquery plugin called noUiSlider. Here is there basic code:

html:

<div id="slider"></div>
<div id="value-input-left" style="font-size:12px"></div>
<div id="value-input-right" style="font-size:12px"></div>

jQuery:

<script>
     $(document).ready(function(){
      $("#slider").noUiSlider({
       start: [20, 80],
       connect: true,
       range: {
       'min': 0,
       'max': 100
        }
     });
      $('#slider').Link('lower').to($('#value-input-left'));
      $('#slider').Link('upper').to($('#value-input-right'));
      alert("return value of range slider" +$("#slider").val());
      });

</script>

The $("#slider").val() returns array[value, value], in this example it's 20.00, 80.00. But what is the easiest way to get their value separately?

For instance, I've tried:$("#slider").val(0); $("#slider").val[0] , $("#slider").lower() and $("#slider").get(0) but none of them works.

The documentation of this plugin is http://ift.tt/1zIPlsa

Thanks!