Word Frequency Count, fix a bug with standard property

Question

I\'m trying to build a javascript function which would count the number of occurrences of each word in an input array.

Example :

Input

a=[\"a         


        

Answer 1

function count(arr){
  return arr.reduce(function(m,e){
    m[e] = (+m[e]||0)+1; return m
  },{});
}

The idea behind are

• the use of reduce for elegance
• the conversion of m[e] to a number using +m[e] to avoid the constructor (or toString) problem

Demonstration

Answer 2

You can also create an array just by initializing [] as the initial accumulator.

var fruits = ['apple', 'orange', 'grape', 'apple'].reduce((countFruits,currentFruit)=>{
  if(typeof countFruits[currentFruit]!=="undefined"){
    countFruits[currentFruit] = countFruits[currentFruit]+1
    return countFruits
  }
  countFruits[currentFruit] = 1
  return countFruits
},[])
console.log(fruits) 

Answer 3

var arr = ['apple', 'orange', 'grape', 'apple'];
var initialValue = {};

var result = arr.reduce(function(accumulator, curr, idx, arr) {
    if (Object.hasOwnProperty.call(accumulator, curr)) {   // does current exist as key on initialValue object?
        accumulator[curr]++;
    } else {    // no key for current on initialValue object
        accumulator[curr] = 1;
    }
    return accumulator;
}, initialValue);

console.log(result);