Tips for finding the common elements in arrays within a nested array

Question

Tips for finding the common elements in arrays within a nested array

I am facing a challenge with an array that was generated by another function and I don't want to make any modifications to it.

var d = [[1, 2, 3], [2, 3], [1, 3]];

My goal is to use the _.intersection method on all arrays within the main array like this:

var c = _.intersection(d);
// expecting to get [3]

However, the _.intersection method requires multiple array parameters as input, not an array of arrays.

I attempted to flatten the array using a similar approach mentioned in Merge/flatten an array of arrays in JavaScript?, but it flattened the entire array into one single array.

var merged = [].concat.apply([], d);    
[1, 2, 3, 2, 3, 1, 3]; // This is not what I want

To provide more context, I have a nested array d (which contains arrays and its length varies). My aim is to find the intersection of all arrays within the array d.

Is there a way for me to dynamically call

_.intersection([1, 2, 3], [2, 3], [1, 3], ...)

based on the contents of array d?

javascript arrays underscore.js

Answer 1

Answer №1

If you're working with ES5, one way to spread the array into parameters is by using Function#apply:

var d = [[1, 2, 3], [2, 3], [1, 3]];

var result = _.intersection.apply(_, d);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

For those using lodash, you can utilize _.spread which converts a function to accept an array of parameters:

var d = [[1, 2, 3], [2, 3], [1, 3]];

var result = _.spread(_.intersection)(d);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

As for ES6 users, the spread syntax provides a concise way to achieve the same outcome:

const d = [[1, 2, 3], [2, 3], [1, 3]];

const result = _.intersection(...d);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

Answer 2

If you're working with ES5, one way to spread the array into parameters is by using Function#apply:

var d = [[1, 2, 3], [2, 3], [1, 3]];

var result = _.intersection.apply(_, d);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

For those using lodash, you can utilize _.spread which converts a function to accept an array of parameters:

var d = [[1, 2, 3], [2, 3], [1, 3]];

var result = _.spread(_.intersection)(d);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

As for ES6 users, the spread syntax provides a concise way to achieve the same outcome:

const d = [[1, 2, 3], [2, 3], [1, 3]];

const result = _.intersection(...d);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

Answer 3

Answer №2

The result you are looking for is not a standard data structure in JavaScript, but you can achieve it by deconstructing the arrays into variables:

let [a,b,c] = [[1, 2, 3], [2, 3], [1, 3]];
console.log(a,b,c);

If you specifically need the desired output as a string, you can do so with the following function:

let d = [
  [1, 2, 3],
  [2, 3],
  [1, 3]
];

function createString(arr) {
  let s = arr.map(el => `[${el}]`).join(", ");
  return `result ${s};`;
}

console.log(createString(d));

Answer 4

The result you are looking for is not a standard data structure in JavaScript, but you can achieve it by deconstructing the arrays into variables:

let [a,b,c] = [[1, 2, 3], [2, 3], [1, 3]];
console.log(a,b,c);

If you specifically need the desired output as a string, you can do so with the following function:

let d = [
  [1, 2, 3],
  [2, 3],
  [1, 3]
];

function createString(arr) {
  let s = arr.map(el => `[${el}]`).join(", ");
  return `result ${s};`;
}

console.log(createString(d));

Answer 5

Answer №3

If you want to access each internal array separately, the best approach is to assign them to individual variables. In ES6, you can easily achieve this by doing:

let d = [[1, 2, 3], [2, 3], [1, 3]];
let [arr1, arr2, arr3] = d;
// -> arr1: [1, 2, 3], arr2: [2, 3], arr3: [1, 3]

Alternatively, you can use the traditional ES5 syntax to accomplish the same task.

If you wish to work with all the internal arrays using a single variable, your only option is to utilize the parent array d.

Answer 6

If you want to access each internal array separately, the best approach is to assign them to individual variables. In ES6, you can easily achieve this by doing:

let d = [[1, 2, 3], [2, 3], [1, 3]];
let [arr1, arr2, arr3] = d;
// -> arr1: [1, 2, 3], arr2: [2, 3], arr3: [1, 3]

Alternatively, you can use the traditional ES5 syntax to accomplish the same task.

If you wish to work with all the internal arrays using a single variable, your only option is to utilize the parent array d.

Tips for finding the common elements in arrays within a nested array

Answer №1

Answer №2

Answer №3

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