Lodash _.intersectionBy() Method

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Lodash is a JavaScript library that works on the top of underscore.js. Lodash helps in working with arrays, strings, objects, numbers, etc.
The _.intersectionBy() is used to take the intersection of the a array with any number of arrays based on some function that iterates over each element of the array. It returns the array after doing intersection of the arrays.

Syntax:

_.intersectionBy([arrays], [iteratee=_.identity])

Parameters:

arrays: It is the array whose intersection has to be taken.
iteratee=_.identity: It is the function that iterates over each element of the array whose intersection is to be taken.

Return Value: It returns the array after intersection with no duplicates.

Note: Please install lodash module by npm install lodash before using the below given code.

Example 1: When Iteratee function is not given it behaves same as intersection() function of the lodash.

javascript

// Requiring the lodash library 
const _ = require("lodash"); 
  
// Original arrays 
let array1 = [1, 2, 4, 3, 4, 4] 
let array2 = [1, 2, 5, 6] 
  
// Using _.intersectionBy() method 
let newArray = _.intersectionBy(array1, array2); 
  
// Printing original Array 
console.log("original Array1: ", array1) 
console.log("original Array2: ", array2) 
  
// Printing the newArray after intersection 
console.log("new Array: ", newArray)  

Output:

Example 2: When Math.ceil() function is used to runs over array1 and all value of array1 are compare to next nearest larger integer and then intersection is taken.

javascript

// Requiring the lodash library 
const _ = require("lodash"); 
  
// Original array and array1  
// float values are given 
let array1 = [1.1, 2.6, 4, 3.2, 1, 2] 
let array2 = [1, 2, 3, 5, 6] 
  
// Using _.intersection() method 
// when this function is run array1 
// looks like array1=[2, 3, 4, 4, 1, 2] 
// after that intersection is taken 
let newArray = lodash.intersectionBy( 
        array1, array2, Math.ceil); 
  
// Printing original Array 
console.log("original Array1: ", array1) 
console.log("original Array2: ", array2) 
  
// Printing the newArray 
console.log("new Array: ", newArray) 

Output:

Example 3: When multiple common elements are present it return them only one times and no duplicates are returned in the array.

javascript

// Requiring the lodash library 
const _ = require("lodash"); 
  
// Original array 
let array1 = ["a", "b", "c", "a"] 
let array2 = ["a", "d", "e", "a"] 
  
// Using _.intersection() method 
let newArray = lodash.intersectionBy( 
        array1, array2, "a"); 
  
// Printing original Array 
console.log("original Array1: ", array1) 
console.log("original Array2: ", array2) 
  
// Printing the newArray 
console.log("new Array: ", newArray) 

Output:

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