CODEWITHSUNDEEP
javascriptarraysintersection
Willyanto Halim
Willyanto Halim

Reputation: 413

intersecting multidimensional array in javascript

let say i have 1 multidimensional array and i want to exclude values that not equal in javascript.

here is the example array.

var filter = ["big_number", "odds_number"];
var arrays = {
    "first" : {
        "big_number" : [50,51,52],
        "odds_number" : [39,41,51,53]
    },
    "second" : {
        "big_number" : [61,62,63,64,65,70,72,73],
        "odds_number" : [13,15,17,19,61,63,65,73]
    }
};

i want to convert that array to be like this.

var new_arrays = {
    "first" : [51],
    "second" : [61,63,65,73]
};

here is my code

var newArray = {
    "first" : [],
    "second" : []
};
for (var k in arrays){
    if (arrays.hasOwnProperty(k)) {
        for(var f=0; f<filter.length; f++) {
            newArray[k].push(arrays[k][filter[f]].filter(value => -1 !== arrays[k][filter[f]].indexOf(value))));
        }
   }
}
console.log(newArray);

actually i could do this code

var newArray = {
    "first" : [],
    "second" : []
};
for (var k in arrays){
    if (arrays.hasOwnProperty(k)) {
        newArray[k].push(arrays[k]["big_number"].filter(value => -1 !== arrays[k]["odds_number"].indexOf(value))));
    }
}
console.log(newArray);

but i need to convert it through filter variable. i could not use filter[0] and filter[1], because that values could change dynamically and could be more than 2 values in array.

Upvotes: 1

Views: 1528

Answers (4)

adiga
adiga

Reputation: 35243

You could loop through the keys and update the values using filter and includes:

var arrays={"first":{"big_number":[50,51,52],"odds_number":[39,41,51,53]},"second":{"big_number":[61,62,63,64,65,70,72,73],"odds_number":[13,15,17,19,61,63,65,73]}};

for (let key in arrays) {
  arrays[key] = arrays[key]["big_number"]
                  .filter(n => arrays[key]["odds_number"].includes(n));
}

console.log(arrays)

If you don't want to mutate the original object then use Object.entries and reduce:

var arrays={"first":{"big_number":[50,51,52],"odds_number":[39,41,51,53]},"second":{"big_number":[61,62,63,64,65,70,72,73],"odds_number":[13,15,17,19,61,63,65,73]}};

const newObject = Object.entries(arrays).reduce((r, [key, {big_number, odds_number}]) => {
  r[key] = big_number.filter(n => odds_number.includes(n));
  return r
}, {})

console.log(newObject)

If you have more than 2 array properties, you can do something like this: Get all the arrays using Object.values and then use reduce to run the previous code recursively 

var arrays = {
  "first": {
    "big_number": [50, 51, 52],
    "odds_number": [39, 41, 51, 53],
    "another_key": [41, 51, 53]
  },
  "second": {
    "big_number": [61, 62, 63, 64, 65, 70, 72, 73],
    "odds_number": [13, 15, 17, 19, 61, 63, 65, 73],
    "another_key": [63, 65]
  }
};

for (let key in arrays) {
  arrays[key] = Object.values(arrays[key])
                       .reduce((a, b) => a.filter(c => b.includes(c)))
}

console.log(arrays)

Upvotes: 2

FZs
FZs

Reputation: 18619

Here is a little intersection snippet: 

function intersect(a,b){
    b.slice()
    return a.filter(item=>{
        if(b.includes(item)){
            b.splice(b.indexOf(item),1)
            return true
        }
    })
}

Using that, you can do this easily: 

function intersect(a,b){
	b.slice()
	return a.filter(item=>{
		if(b.includes(item)){
			b.splice(b.indexOf(item),1)
			return true
		}
	})
}

var filter = ["big_number", "odds_number"];
var output={}
var arrays = {
    "first" : {
        "big_number" : [50,51,52],
        "odds_number" : [39,41,51,53]
    },
    "second" : {
        "big_number" : [61,62,63,64,65,70,72,73],
        "odds_number" : [13,15,17,19,61,63,65,73]
    }
};
for(x in arrays){
    output[x]=arrays[x][filter[0]]
    for(let i=1;i<filter.length;i++){
        output[x]=intersect(output[x],arrays[x][filter[i]])
    }
}
console.log (output)

Upvotes: 1

Hassan Imam
Hassan Imam

Reputation: 22554

You can get the unique values from both the arrays using Set and then using filter get only the common values.

var arrays = {"first": {"big_number": [50, 51, 52],"odds_number": [39, 41, 51, 53]},"second": {"big_number": [61, 62, 63, 64, 65, 70, 72, 73],"odds_number": [13, 15, 17, 19, 61, 63, 65, 73]}},
    result = Object.keys(arrays).reduce((r,k) => {
      let setB = new Set(arrays[k]["big_number"]);
      r[k] = [...new Set(arrays[k]["odds_number"])].filter(x => setB.has(x));
      return r;
    },{});
console.log(result)
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 0

random
random

Reputation: 7901

use Object.entries to get keys and values and then use reduce 

var arrays = {
  "first" : {
      "big_number" : [50,51,52],
      "odds_number" : [39,41,51,53]
  },
  "second" : {
      "big_number" : [61,62,63,64,65,70,72,73],
      "odds_number" : [13,15,17,19,61,63,65,73]
  }
};

const output =Object.entries(arrays).reduce((accu, [key, {big_number}]) => {
  if(!accu[key]) accu[key] = [];
  big_number.forEach(num => {
    if(num%2 !==0)
    accu[key].push(num);
  })
  return accu;
}, {});

console.log(output);

Upvotes: 0

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