Lodash _.transform() Method

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Lodash is a JavaScript library that works on the top of underscore.js. Lodash helps in working with arrays, collection, strings, lang, function, objects, numbers etc.
The _.transform() method is an alternative to _.reduce() method transforms object to a new accumulator object which is the result of running each of its own enumerable string keyed properties through iteratee with each invocation potentially mutating the accumulator object. A new object with the same prototype will be used if an accumulator is not provided.
Syntax:

_.transform(object, iteratee, accumulator)

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

object: It holds the object to iterate over.
iteratee: It is the function that the method invoked per iteration for every element.
accumulator: It holds the custom accumulator value.

Return Value: This method returns the accumulated value.
Example 1: Here, const _ = require(‘lodash’) is used to import the lodash library in the file.

javascript

// Requiring the lodash library 
const _ = require("lodash"); 
 
// Original array 
var object = [12, 13, 14];     
 
// Using the _.transform() method
let st_elem = _.transform(object, 
            function(result, n) {
  result.push(n *= n);
  return n % 2 == 0;
}, []);
 
 
// Printing the output 
console.log(st_elem);

Output:

144, 169

Example 2:

javascript

// Requiring the lodash library 
const _ = require("lodash"); 
 
// Original array 
var object = { 'p': 3, 'q': 6, 'r': 3 };     
 
// Using the _.transform() method
let st_elem = _.transform(object, 
    function(result, value, key) {
  (result[value] || (result[value] = [])).push(key);
}, {});
 
 
// Printing the output 
console.log(st_elem);