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Lodash is a popular JavaScript utility library that provides a wealth of utility functions to simplify common programming tasks. It helps developers handle data structures such as arrays, objects, strings, and provides great help in performance and code simplicity. Lodash provides many practical methods, such as deep copy, deduplication, sorting, merging, searching, etc. These operations may require a lot of code in JavaScript, but using Lodash can greatly simplify these operations.

1. Install Lodash​

First, you can install Lodash in your project with the following command:

npm i --save lodash

After the installation is complete, Lodash can be used in JavaScript or TypeScript files.

2. Import Lodash​

There are usually two ways to introduce Lodash in a project:

a. Import the entire Lodash library​

import _ from 'loadash'
const _ = require('lodash');

This can reduce the bundle size of the project because only the required functions are imported.

const isEmpty = require('lodash/isEmpty');
const cloneDeep = require('lodash/cloneDeep');

3. Common Lodash functions and code examples​

Below are some common Lodash functions and usage examples.

3.1 _.cloneDeep - Deeply clone objects​

cloneDeep is used to deeply clone objects or arrays to ensure that the copied objects and the original objects do not affect each other.

const _ = require('lodash');

const original = { a: 1, b: { c: 2 } };
const copy = _.cloneDeep(original);

copy.b.c = 3;
console.log(original.b.c); // Output 2, the original object is unchanged
console.log(copy.b.c); // Output 3

3.2 _.isEmpty - Check if an object or array is empty​

isEmpty is used to check if an object, array or string is empty.

const _ = require('lodash');

console.log(_.isEmpty([])); // Output true
console.log(_.isEmpty({})); // Output true
console.log(_.isEmpty({ a: 1 })); // Output false

3.3 _.uniq - Remove duplicate values ​​from an array​

uniq is used to remove duplicate values ​​from an array and return a new array.

const _ = require('lodash');

const arr = [1, 2, 2, 3, 4, 4, 5];
const uniqueArr = _.uniq(arr);

console.log(uniqueArr); // output [1, 2, 3, 4, 5]

3.4 _.merge - Merge objects​

merge can recursively merge objects. When two objects have the same key, the value of the latter will overwrite the value of the former.

const _ = require('lodash');

const obj1 = { a: 1, b: { c: 2 } };
const obj2 = { b: { d: 3 }, e: 4 };
const mergedObj = _.merge(obj1, obj2);

console.log(mergedObj); // output { a: 1, b: { c: 2, d: 3 }, e: 4 }

3.5 _.find - Find an object in an array​

find is used to find the first element in an array that meets a condition.

const _ = require('lodash');

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' },
];

const user = _.find(users, { name: 'Bob' });
console.log(user); // output { id: 2, name: 'Bob' }

4. Lodash combination usage example​

Suppose we have an array of user data, and we need to find users older than 25, sort these users by age, and then take the first two.

const _ = require('lodash');

const users = [
  { name: 'Alice', age: 28 },
  { name: 'Bob', age: 22 },
  { name: 'Charlie', age: 30 },
  { name: 'David', age: 26 },
];

// Filter, sort and take the first two
const result = _(users)
  .filter(user => user.age > 25)
  .sortBy('age')
  .take(2)
  .value();

console.log(result);
// output  [{ name: 'David', age: 26 }, { name: 'Alice', age: 28 }]

Summary​

Lodash provides a wealth of utility functions that can greatly simplify code writing and improve code readability and performance. In large projects, using Lodash can also improve code maintainability.

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