Can I have an object key as part of an array?-CodePudding

I am trying to sort some numbers, and I want to count the number of times that an array has a certain number.

My question is more about the structure of an the array than the counting the number part. I would like to build an array that looks like this below.

let numbers = [1,2,3,4,4,4,5,5,6];

How could I make the data structure below?

numbers[3].count // this will be equal to 3 after I loop through;

How do I make each part of the array have an object parameter?

Do I just loop through like so?

for (let i = 0; i < numbers.length; i  ){
  numbers[i] = {
    count: 0
  }
}

I understand this wont give me the right count, but I don't care about that part of the problem. I would like to solve that on my own. I just need to be sure that this is the correct way to add the object parameters.

CodePudding user response：

I would build these functions on my own. Something like this You can copy and paste this in the console of your browser.

// my numbers list
const numbers = [1, 2, 3, 4, 4, 4, 5, 5, 6];
// reduced to unique entries
const uniques = [...new Set(numbers)];
// function to count occurrences in my list of number
const count = (n) => numbers.filter((num) => num === n).length;
// you can test here
console.log(`counting ${uniques[4]}s`, count(uniques[4]));
// get these as object
console.log(uniques.map((unique) => ({[unique]: count(unique)})))

CodePudding user response：

Simplest way to achieve this by using Array.forEach().

let numbers = [1,2,3,4,4,4,5,5,6];

const obj = {};

numbers.forEach((item) => {
    obj[item] = (obj[item] || 0)   1;
});

console.log(obj);

CodePudding user response：

const numbers = [1,2,3,4,4,4,5,5,6];

const counts = {};

numbers.forEach((x) => counts[x] = (counts[x] || 0) 1);

console.log(counts)

CodePudding user response：

Reduce is perfect for these kinds of problems.

const numbers = [1,2,3,4,4,4,5,5,6];

const countedObject = numbers.reduce((tmpObj, number) => {
  if (!tmpObj[number]) {
    tmpObj[number] = 1;
  } else {
    tmpObj[number]  = 1;
  }
  return tmpObj
}, {});


console.log(countedObject);

if you feel the need to nest it further you can of course do this. But if count is the only property you need, I'd suggest sticking to the first version.

const numbers = [1,2,3,4,4,4,5,5,6];

const countedObject = numbers.reduce((tmpObj, number) => {
  if (!tmpObj[number]) {
    tmpObj[number] = {count: 1};
  } else {
    tmpObj[number].count  = 1;
  }
  return tmpObj
}, {});


console.log(countedObject);