Lodash _.sumBy() 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 _.sumBy() method is used to compute the sum from the original array by iterating over each element in the array by using the Iteratee function. It is almost the same as _.sum() method.

Syntax:

_.sumBy(array, [iteratee = _.identity])

Parameters: This method accepts two parameters as mentioned above and described below:

array: This parameter holds the array to iterate over.
[iteratee = _.identity]: This parameter holds the iteratee invoked per element.

Return Value: This method returns the sum.

Example 1: Here, const _ = require(‘lodash’) is used to import the lodash library into the file.

Javascript

// Requiring the lodash library   
const _ = require("lodash");   
   
// Original array  
var arr = [{ 'n': 4 }, { 'n': 2 }, { 'n': 6 }]; 
     
// Use of _.sumBy()   
// method  
let gfg = _.sumBy(arr, function(o) { return o.n; });  
         
// Printing the output   
console.log(gfg);

Output:

Example 2:

Javascript

// Requiring the lodash library   
const _ = require("lodash");   
   
// Original array  
var arr = [{ 'n': 10 }, { 'n': 5 }, { 'n': 3 }, { 'n': 12 }]; 
     
// Use of _.sumBy()   
// method  
let gfg = _.sumBy(arr, 'n');  
         
// Printing the output   
console.log(gfg);