Pipe and Reduce implementation

PipeandReduce.js

let statement  = "wELCOME | lower | capitalize";
let another =  "welcome | upper";

let handlers = {
  lower : (val) => val.toLowerCase(),
  upper: (val) => val.toUpperCase(),
  capitalize: (val) => val.slice(0,1).toUpperCase() + val.slice(1)
  
};

function parseStatement(statement)
{
   let pieces = statement.split("|").map(piece => piece.trim())
   
   let needle = pieces.shift();
  
   let result = pieces.reduce((value , handlerName) =>
   {
         return handlers[handlerName](value);
   } , needle);
  
  console.log(result);
  
}


parseStatement(statement);
parseStatement(another);



function customReduce(list , handler , initial=false)
{
    var len = list.length;
    var  curResult;
    for(var i = 0; i < len; i++)
    {
            if(initial) {
              
               if(i == 0){
                 
                  var curResult = handler.call(this , initial , list[i]);
               }else {
                 var curResult = handler.call(this , curResult , list[i]);
               }
        
            }else{
              if(i == 0) {
                var curResult = handler.call(this , list[i] , list[i + 1]);
                i += 1;
              }
              else{
                var curResult = handler.call(this, curResult , list[i]);
              }
            }
    }
  
  console.log(curResult);
}


let list = [1,2,3,4,5];
let handler = (a,b) =>
{
    return a + b;
};
customReduce(list ,handler , 20);
customReduce(list , handler);