reduce in typescipt

 calculate sum of the amount use below logic

this.TotalAmount=  res.reduce((total, current) => total +

(current.Quantity * current.UnitPrice), 0);

i have two arrays need to loop those and and description.

intad of getting data usign joins i have using below logic to add description ot items list

 if(this.lstGlcode.length >0){

            res.forEach(y=>{

              let gldesc=this.lstGlcode.find(x=>x.Id === y.GldescriptionId)

              if(gldesc){

                y.GlDescription=gldesc.Description;

              }

            })

        }