Filter and Sort an Object Containing Array of Objects While Retaining Empty Arrays

Question

I have an object I want to filter so that trainers with the most electric-type pokemon are listed first, but trainers without any electric-type pokemon are still present (represented as an empty array)

Here's my object:

obj = {
  trainer1: [ 
    { name: 'pikachu', type: 'electric', id: 25 },
    { name: 'zapdos', type: 'electric', id: 145 },
    { name: 'psyduck', type: 'water', id: 54 },
  ],
  trainer2: [
    { name: 'eevee', type: 'normal', id: 133 },
    { name: 'magmar', type: 'fire', id: 126 }
  ],
  trainer3: [
    { name: 'ditto', type: 'normal', id: 132 },
    { name: 'magnemite', type: 'electric', id: 81 }
  ]
}

Becomes this object:

obj = {
  trainer1: [ 
    { name: 'pikachu', type: 'electric', id: 25 },
    { name: 'zapdos', type: 'electric', id: 145 }
  ],
  trainer3: [
     { name: 'magnemite', type: 'electric', id: 81 }
  ]
  trainer2: [] // Array still present, but empty
}

I know reduce would come in handy here but I'm not sure how to set it up correctly.

Answer 1

This may be the bruteforce solution and there will be better solution than this but i think you can do it like the following way.

const tempArr = Object.keys(obj).map(key=>{
  return {
     key:key,
     value:obj[key].filter(pokemon=>pokemon.type==='electric')
  }
})

let newObj = {}
tempArr.sort((a,b)=>b.value.length-a.value.length)

tempArr.forEach(item=>{
  newObj[item.key] = item.value
})

console.log(newObj)