javascript - how to access zeroth element in reduce to count repeats in an array -

on whim of node school, trying use reduce count number of times string repeated in array.

var fruits = ["apple", "banana", "apple", "durian", "durian", "durian"],     obj = {}; fruits.reduce(function(prev, curr, index, arr){    obj[curr] ? obj[curr]++ : obj[curr] = 1; }); console.log(obj); // {banana: 1, apple: 1, durian: 3} 

is sort of working. reason, reduce seems skip first element. don't know why. first time through array, index 1. tried putting in logic like, if (index === 1){//put 'prev' property of 'obj'}. seems convoluted. i'm not how node school wants me solve problem. however, wonder what's way access zeroth element in array you're reducing. why zeroth element seemingly ignored reduction procedure? guess pass in fruits[0] after callback start value initially. what's best way access zeroth element?

if no initialvalue provided, previousvalue equal first value in array , currentvalue equal second.

https://developer.mozilla.org/en-us/docs/web/javascript/reference/global_objects/array/reduce#description

additionally, have return value function. value becomes value of previousvalue on next iteration.

i'd suggest "carry" aggregator obj initial value.

var fruits = ["apple", "banana", "apple", "durian", "durian", "durian"];  var obj = fruits.reduce(function(carry, fruit){    if(!carry[fruit]) carry[fruit] = 0; // if key doesn't exist, default 0    carry[fruit]++;                     // increment value of key    return carry;                       // return aggregator next iteration  }, {});  alert(json.stringify(obj));

here's simple diagram:

               fruit  carry (before operation)      carry (after operation, returned value) 1st iteration: apple  {}                            {apple:1} 2nd iteration: banana {apple:1}                     {apple:1, banana:1}  3rd iteration: apple  {apple:1, banana:1}           {apple:2, banana:1} 4th iteration: durian {apple:2, banana:1}           {apple:2, banana:1, durian:1} 5th iteration: durian {apple:2, banana:1, durian:1} {apple:2, banana:1, durian:2} 6th iteration: durian {apple:2, banana:1, durian:2} {apple:2, banana:1, durian:3}