JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr=[18, 15, 11, 8, 2, 1, 0];
        //var arr=[96448, 35780];         
          var diff=[];
          $.each(arr,function(i,v){
           //96448 - 35780 = 60668 / 96448 = 0,629 * 100 = 62,9%
           if(i==arr.length-1){
            diff.push('---');
            return;
           }
           var first=v;
           var second=arr[i+1];
             var calc =( 100 - ((first - second)/first)*100).toFixed(2)+'%';
             diff.push(calc);
          });
          alert(diff);