Finding intersection between 2 arrays of objects with dynamic keys

Question

I have 2 arrays of objects with dynamic keys (i never know the name of the key); Example:

hierarchy1: [
  {
    level1: 'Shoes',
  }
]

hierarchy2: [
  {
    level1: 'Shoes',
    level2: 'Sneakers',
  },
]

I need to find intersection between hierarchy1 and hierarchy2. I can't use lodash _.intersectionBy because i dont know the name of the key i will get in hierarchy1.

I'd expect to get the result like this [{ level1: 'Shoes' }] Any ideas how to solve this issue?

Thanks a lot!

Answer 1

if you want to compare with every index then you can do something like this

const hierarchy1 = [{
  level1: 'Shoes',
  level3: "xyz"
}]

const hierarchy2 = [{
  level1: 'Shoes',
  level2: 'Sneakers',
}, {
  level3: "xyz"
}]

function intersection(arr1, arr2) {
  let final = []
  // loop over first array
  for (let i = 0; i < arr1.length; i++) {
    let element = arr1[i]
    let temp = {}
    
    // loop over all indexes of second array
    for (let data of arr2) {
      // check every key fro data to see if there's any intersection
      Object.keys(data).forEach(key => {
        if (data[key] === element[key] && key in element) {
          temp[key] = element[key]
        }
      })
    }
    // if we found any intersection push it in final array
    if (Object.keys(temp).length) {
      final.push(temp)
    }
  }
  return final
}

console.log(intersection(hierarchy1, hierarchy2))

an improvement to first approach is doing some pre-calculations, you can simply club all the values for a particular key and when looping over you can check if there's particular value present for the given key or not

const hierarchy1 = [{
  level1: 'Shoes',
  level3: "xyz"
},{level2: "abc"}]

const hierarchy2 = [{
  level1: 'Shoes',
  level2: 'Sneakers',
}, {
  level3: "xyz",
  level2: "abc"
}]

function intersection(arr1, arr2) {
  let final = []
  let map = {}
  for(let data of arr2){
    Object.keys(data).forEach(key => {
      map[key] = map[key] || new Set()
      map[key].add(data[key])
    })
  }
  // loop over first array
  for (let i = 0; i < arr1.length; i++) {
    let element = arr1[i]
    let temp = {}
    Object.keys(element).forEach(key => {
      if (key in map && map[key].has(element[key])) {
         temp[key] = element[key]
      }
    })
    // if we found any intersection push it in final array
    if (Object.keys(temp).length) {
      final.push(temp)
    }
  }
  return final
}

console.log(intersection(hierarchy1, hierarchy2))

If you just want to compare respective indexes or both array you can do something like this

const hierarchy1 = [{
  level1: 'Shoes',
}]

const hierarchy2 = [{
  level1: 'Shoes',
  level2: 'Sneakers',
},]

function intersection(arr1,arr2){
  let final = []
  for(let i=0; i<arr1.length; i++){
    let element = arr1[i]
    let temp = {}
    Object.keys(element).forEach(key => {
       if(key in arr2[i] && arr2[i][key] === element[key]){
         temp[key] = element[key]
       }
    })
    if(Object.keys(temp).length){
      final.push(temp)
    }
  }
  return final
}

console.log(intersection(hierarchy1,hierarchy2))