Appending new keys, and changing values in for/if loop

user_15780618 0
Viewed 21

My current goal is to take items in array integers and create a key pair value based on how many times the key appeared in integers. My logic is: for i in integers, if i is in integers 2 already, increment that key's value by 1. if it doesn't exist, create the key and pair it with a value of 1. It's been a few hours now and after heavy googling I can't seem to find where im messing my logic up.

//require realdine-sync module
var readlineSync = require('readline-sync');
//initialize variable and list
var integer;
integers2 = {};
var integers = [];
//user input
integer = readlineSync.question('Integer?: ')
//check user input and append any integer besides 0
while (integer != 0 && integer >= 1 && integer <= 100){
console.log("not 0!")
integers.push(integer)
integer = readlineSync.question('Integer?: ')
}
console.log(integers);
for(i in integers){if (i in integers2){integers2[i] += 1}else{integers2[i] = 1}
   
}
console.log(integers2)
append dictionary javascript
2 Answers

let integers2 = {}

integers = [5, 4, 5, 2, 4, 7, 5];

// you were using 'in' instead 'of', 'in': gives you index , 'of'?: gives you value of array
for (let i of integers) {
    if (integers2[i]) { // if key exist increment value by one
        integers2[i] += 1
    } else { // else add 1 as the first value
        integers2[i] = 1
    }
}
console.log(integers2);

user_63847760

This is a solution that you can try which works. It uses the same logic as you described in the question. This solution uses Array.prototype.reduce() with a Map().

const howMany = arr => arr
  .reduce(
    (map, n) => map.set(n, (map.get(n) ?? 0) + 1), 
    new Map()
  )

console.log([...howMany([3, 4, 6, 4, 5, 5, 5])])

user_111454470
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