group array and get count

Question

Say I have array like this:

[
   \"foo\",
   \"bar\",
   \"foo\"
   \"bar\",
   \"bar\",
   \"bar\",
   \"zoom\"
]

I want to group it so I

Answer 1

Explanation: First, we create object (a brand new empty object). Secondly using the spread operator we first copy everything from the existing array and make a new array out of it and use that to create a new Set (the Set object lets you store unique values) and use that as the key, and finally we filter out our array (with a little help from the length property) to see how many times a particular key occurs and set that to the object's value. And remember, since we used Object.assign() and put everything inside of it, so what gets returned is an object containing the result of everything that I tried to explain (to the best of my knowledge) above :) We also used the comma operator here which simply evaluates each of its operands (from left to right) and returns the value of the last operand.

const arr = ["foo", "bar", "foo", "bar", "bar", "bar", "zoom"];

const data = Object.assign({}, ...Array.from(new Set(arr), key => ({[key]: arr.filter(value => value === key).length})));

console.log(data);