Lodash _.transform() Method

Lodash _.transform() method is an alternative to the _.reduce() method transforms an 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:

• 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: In this example, we are transforming the given array by the use of the lodash _.transform() method.

javascript

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

// Original array
let 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: In this example, we are transforming the given array by the use of the lodash _.transform() method.

javascript

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

// Original array
let 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);

Output:

{ '3': ['p', 'r'], '6': ['q'] }

Note: This code will not work in normal JavaScript because it requires the library lodash to be installed.