Javascript array.filter and reduce

Question

Turn an array of voter objects into a count of how many people voted Please help me i starting learn javascript but i'm so confused with reduce and filter some one can fix ? I run code and undefined @@``

    function total(arr) {
    let result = arr.filter(function(votes){
   return votes !==true;
 }).reduce(function(item,cur){
   return [(+item),+(+cur)];
 },[0]);}
var voters = [
  {name:'Bob' , age: 30, voted: true},
  {name:'Jake' , age: 32, voted: true},
  {name:'Kate' , age: 25, voted: false},
  {name:'Sam' , age: 20, voted: false},
  {name:'Phil' , age: 21, voted: true},
  {name:'Ed' , age:55, voted:true},
  {name:'Tami' , age: 54, voted:true},
  {name:'Mary', age: 31, voted: false},
  {name:'Becky', age: 43, voted: false},
  {name:'Joey', age: 41, voted: true},
  {name:'Jeff', age: 30, voted: true},
  {name:'Zack', age: 19, voted: false}
];``

voters.filter(x=>x.voted).length

dandavis
– dandavis

2019-10-07 22:07:14 +00:00
Commented Oct 7, 2019 at 22:07 — dandavis
– dandavis, Commented Oct 7, 2019 at 22:07
thanks everyone i just do it :D

Toàn Phương
– Toàn Phương

2019-10-08 17:43:55 +00:00
Commented Oct 8, 2019 at 17:43 — Toàn Phương
– Toàn Phương, Commented Oct 8, 2019 at 17:43

Jose · Accepted Answer · 2019-10-07 22:04:52Z

1

the best and shortest way to do it, just filter and count

let voters = [
  {name:'Bob' , age: 30, voted: true},
  {name:'Jake' , age: 32, voted: true},
  {name:'Kate' , age: 25, voted: false},
  {name:'Sam' , age: 20, voted: false},
  {name:'Phil' , age: 21, voted: true},
  {name:'Ed' , age:55, voted:true},
  {name:'Tami' , age: 54, voted:true},
  {name:'Mary', age: 31, voted: false},
  {name:'Becky', age: 43, voted: false},
  {name:'Joey', age: 41, voted: true},
  {name:'Jeff', age: 30, voted: true},
  {name:'Zack', age: 19, voted: false}
];

voters.filter(person => person.voted).length

answered Oct 7, 2019 at 22:04

Jose

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Comments

Nina Scholz · Accepted Answer · 2019-10-07 22:00:59Z

You could take a single reduce and add simply the boolean value of the object to the count.

function total(array) {
    return array.reduce(function(count, voter) {
        return count + voter.voted;
    }, 0);
}

var voters = [{ name: 'Bob', age: 30, voted: true }, { name: 'Jake', age: 32, voted: true }, { name: 'Kate', age: 25, voted: false }, { name: 'Sam', age: 20, voted: false }, { name: 'Phil', age: 21, voted: true }, { name: 'Ed', age:55, voted: true }, { name: 'Tami', age: 54, voted: true }, { name: 'Mary', age: 31, voted: false }, { name: 'Becky', age: 43, voted: false }, { name: 'Joey', age: 41, voted: true }, { name: 'Jeff', age: 30, voted: true }, { name: 'Zack', age: 19, voted: false }];

console.log(total(voters));

Nick · Accepted Answer · 2022-11-15 14:46:49Z

-1

Here is one way you could solve the problem:

console.log(voters.reduce((prev,curr,i,ar)=>{
    (curr.voted==true && curr.age >=18) ?  ans.push(curr) : null
    return ans.length
},{}))

edited Nov 15, 2022 at 14:46

Nick

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answered Nov 15, 2022 at 13:21

harith

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