Lodash _.differenceBy() Method

Lodash _.differenceBy() method is used to remove the values from the original array by iterating over each element in the array by using the Iterate function. It is almost same as _.difference() function.

Syntax:

lodash.differenceBy(array, [values], [iterate=_.identity])

mentionedParameters:

This function accepts three parameters as mentioned above and described below

• array: This is the array from which the values are to be removed.
• values: It is the Array of values that is to be removed from the original array.
• Iterate: This is the function that iterate over each element.

Note: If the iterate function is not given then _.differenceBy() function act as _.difference() function.   

Return Value:

This function returns an array. 

Example 1: In this example, we use the lodash library to subtract one array (val) from another (array1).

Javascript

// Requiring the lodash library
const _ = require("lodash");

// Original array
let array1 = [1, 2, 3, 4.2]

// Array to be subtracted
let val = [2, 3, 3, 5]

// New Array after _.differenceBy()
// method where Math.double is the
// comparable function
let newArray = _.differenceBy(
    array1, val, Math.double);

// Printing the original array
console.log("Before : ", array1);

// Printing the output
console.log("After : ", newArray);

Output:

Example 2: In this example, we use lodash library to find differences between arrays, with and without a custom comparator function.

Javascript

// Requiring the lodash library
const _ = require("lodash");

// Original array
let array1 = [1, 2, 3, 4.2]

// Value array to be subtracted
let val = [2, 3, 4, 5]

// new Array after _.differenceBy()
// method where Math.double is the
// comparable function
let newArray1 = _.differenceBy(
    array1, val, Math.floor);

// New Array after _.differenceBy function
// where no comparable function is given
let newArray2 = _.differenceBy(array1, val);

// Printing the original array
console.log("Before : ", array1);

// printing the output
console.log("When compare funct is given: ",
        newArray1);

// Printing the output
console.log("When compare funct is not given: ",
        newArray2);

Output: