Make an array from multiple arrays with common objects

Question

I have the following json which is an array with 2 nested arrays:

[
  [
          {
            "name": "WalkBack",
            "frameRate": 15
          },
          {
            "name": "WalkFront",
            "frameRate": 15
          },
          {
            "name": "WalkLeft",
            "frameRate": 15
          },
          {
            "name": "WalkRight",
            "frameRate": 15
          },
          {
            "name": "Laughing",
            "frameRate": 15
          },
          {
            "name": "Megaphone",
            "frameRate": 15
          },
          {
            "name": "Yawning",
            "frameRate": 15
          }
        ],
        [
          {
            "name": "WalkBack",
            "frameRate": 15
          },
          {
            "name": "WalkFront",
            "frameRate": 15
          },
          {
            "name": "WalkLeft",
            "frameRate": 15
          },
          {
            "name": "WalkRight",
            "frameRate": 15
          }
        ]
]

I need to make a new array of the common object names seen in both arrays like this:

[{
            "name": "WalkBack"
          },
          {
            "name": "WalkFront"
          },
          {
            "name": "WalkLeft"
          },
          {
            "name": "WalkRight"
          }]

So in this case the walk animations are the common names. I tried using:

result = firstArray.filter(o => secondArray.some(({name}) => o.name === name));

but this only works if you know have names for the inner arrays. Any ideas?

I answered but please tell me if I understood your problem correctly — djcaesar9114
– djcaesar9114, Commented Jun 6, 2020 at 11:58

rishichawda · Accepted Answer · 2020-06-06 12:51:38Z

1

Simplest would be to use the reduce method on them by taking first array as a reference. Something like this:

const data=[[{name:"WalkBack",frameRate:15},{name:"WalkFront",frameRate:15},{name:"WalkLeft",frameRate:15},{name:"WalkRight",frameRate:15},{name:"Laughing",frameRate:15},{name:"Megaphone",frameRate:15},{name:"Yawning",frameRate:15}],[{name:"WalkBack",frameRate:15},{name:"WalkFront",frameRate:15},{name:"WalkLeft",frameRate:15},{name:"WalkRight",frameRate:15}]];

const [refArr, ...rest] = data

const formattedData = refArr.reduce((commons = [], item) => {
  let isCommon = rest.every(arr => arr.some(itemInArr => item.name === itemInArr.name))
  return isCommon ? [...commons, item] : commons
}, [])

console.log(formattedData)

edited Jun 6, 2020 at 12:51

answered Jun 6, 2020 at 12:14

rishichawda

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4 Comments

Andrew Howard Over a year ago

Thanks for your answer but that's still including the uncommon object names such as "Laughing" and "Megaphone".

rishichawda Over a year ago

Sorry about that. I have updated my answer. It will work on any size of an array.

Andrew Howard Over a year ago

Thanks, would this still work if there are more than 2 inner arrays?

rishichawda Over a year ago

It is also cross-browser compatible since it uses only reduce, some, and every prototype methods. If you try to use flat to flatten them first and then process it, it would break in IE (unless you are poly filling). But, I would rather prefer what is available than adding more code to the bundle. :)

Rajneesh · Accepted Answer · 2020-06-06 12:14:52Z

1

First you can flat your data then you reduce it and filter out records by checking length, if it has more than one value.

var data=[ [ { "name": "WalkBack", "frameRate": 15 }, { "name": "WalkFront", "frameRate": 15 }, { "name": "WalkLeft", "frameRate": 15 }, { "name": "WalkRight", "frameRate": 15 }, { "name": "Laughing", "frameRate": 15 }, { "name": "Megaphone", "frameRate": 15 }, { "name": "Yawning", "frameRate": 15 } ], [ { "name": "WalkBack", "frameRate": 15 }, { "name": "WalkFront", "frameRate": 15 }, { "name": "WalkLeft", "frameRate": 15 }, { "name": "WalkRight", "frameRate": 15 } ]];

var result2 =  Object.entries(data.flat().reduce((acc, {name})=>{
   acc[name] = [...(acc[name] || []),{name}];
   return acc;
},{})).filter(([k,v])=>v.length>1).map(([name])=>({name}));

console.log(result2);

edited Jun 6, 2020 at 12:14

answered Jun 6, 2020 at 12:01

Rajneesh

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4 Comments

Andrew Howard Over a year ago

Thanks for your answer but this is somewhat hard-coded to know that there are always 2 arrays. It could be 2 or more. Anyway to automate it more?

Rajneesh Over a year ago

@AndrewJuniorHoward, I have edited my answer let me know if this helps you.

Andrew Howard Over a year ago

Thanks I'm just having trouble using .flat(). I'm just trying to get my typescript to allow it.

Andrew Howard Over a year ago

Perfect! Thank you so much, there's no way I would have guessed all that :)

djcaesar9114 · Accepted Answer · 2020-06-06 12:08:40Z

First you gather all the "names", then you filter the duplicates :)

var arrays = [
  [
          {
            "name": "WalkBack",
            "frameRate": 15
          },
          {
            "name": "WalkFront",
            "frameRate": 15
          },
          {
            "name": "WalkLeft",
            "frameRate": 15
          },
          {
            "name": "WalkRight",
            "frameRate": 15
          },
          {
            "name": "Laughing",
            "frameRate": 15
          },
          {
            "name": "Megaphone",
            "frameRate": 15
          },
          {
            "name": "Yawning",
            "frameRate": 15
          }
        ],
        [
          {
            "name": "WalkBack",
            "frameRate": 15
          },
          {
            "name": "WalkFront",
            "frameRate": 15
          },
          {
            "name": "WalkLeft",
            "frameRate": 15
          },
          {
            "name": "WalkRight",
            "frameRate": 15
          }
        ]
]

var names = []
arrays.forEach(function(array) {
  array.forEach(function(item) {
    names.push(item.name)
  })
})

var result = []
names.filter( (x,i,a) => a.slice(0,i).find(y=>y==x)  ).forEach(x=>result.push({name: x}))
console.log(result)

ABGR · Accepted Answer · 2020-06-06 12:28:21Z

var arr = [
  [
          {
            "name": "WalkBack",
            "frameRate": 15
          },
          {
            "name": "WalkFront",
            "frameRate": 15
          },
          {
            "name": "WalkLeft",
            "frameRate": 15
          },
          {
            "name": "WalkRight",
            "frameRate": 15
          },
          {
            "name": "Laughing",
            "frameRate": 15
          },
          {
            "name": "Megaphone",
            "frameRate": 15
          },
          {
            "name": "Yawning",
            "frameRate": 15
          }
        ],
        [
          {
            "name": "WalkBack",
            "frameRate": 15
          },
          {
            "name": "WalkFront",
            "frameRate": 15
          },
          {
            "name": "WalkLeft",
            "frameRate": 15
          },
            {
            "name": "WalkRight",
            "frameRate": 15
          }
        ]
];
debugger;
var arr1 = arr[0], arr2 = arr[1],
myObj = {};
arr1.forEach(i=>{
 if(!myObj[i.name]){
   myObj[i.name] = true;
 }
}
);

arr2.forEach(i=>{
 if(!myObj[i.name]){
   delete myObj[i.name]
 }
})

console.log(myObj)

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