Playing with array.reduce()
// I think "accumulated" is a better name than "accumulator". // This arg is the value that's been accumulated, not a // long-lasting a thing that accumulates stuff. let arr = [11,22,33] arr.reduce((accumulated, current)=>(accumulated + current)) >>66 // The first call to your function uses the first AND SECOND array elements arr.reduce((accumulated, current)=>{console.log(accumulated + ' ' + current); return 'hi'}) 11 22 hi 33 >>"hi" // ...unless you provide a second arg to Array.reduce itself. If you do, then // that second arg will be passed as accumulated on the first call of your function. // And that also means that the first call no longer consumes two elements. arr.reduce((accumulated, current)=>{console.log(accumulated + ' ' + current); return 'hi'}, 1000) 1000 11 hi 22 hi 33 >>"hi" // Using the second arg is safer. Without it, and empty array does this: ar