How to import libraries in javascript

With the widespread application of JavaScript in Web development, we not only need to master basic syntax and semantics, but also need to have an in-depth understanding of its underlying principles and advanced techniques. When building powerful applications, using existing JavaScript libraries and frameworks can help speed up the development process and improve code quality and performance.

This article will introduce how to use and import libraries in JavaScript.

What is a JavaScript library?

JavaScript libraries are bits of code shared by developers. Developers can use these codes to speed up application development and avoid duplicating similar code.

Libraries can contain various types of code such as objects, functions, classes, constants, etc. They provide commonly used operations and functions, and developers can easily integrate them into their own applications. These libraries allow developers to improve applications faster and provide a better user experience.

How to use JavaScript library?

The use of JavaScript libraries is very simple. You only need to import the library in your code and call the functions or objects in the library when needed.

Before the ES6 standard, using JavaScript libraries required finding the required library files online, and then introducing the library files into the HTML page through the <script></script> tag. Like this:

<script></script>

In the ES6 standard, using the concept of module, JavaScript supports directly importing and using libraries. Through the import and export keywords, developers can very conveniently import libraries from a file or component, for example:

import { someFunction } from ‘path-to-library/library.js’;

so that we can use someFunction to complete the operations we need.

Commonly used JavaScript libraries

Currently, there are many excellent libraries to choose from in the JavaScript community. These libraries can help us solve common problems, such as data visualization, DOM manipulation, etc. The following are some of the commonly used JavaScript libraries.

1. jQuery

jQuery is a popular JavaScript library that provides simplified DOM operations, animation effects, event handling and other functions. Because it is widely used, it has strong community support and plenty of resources.

When using jQuery, just introduce the library through the <script></script> tag. For example:

<script></script>

The method of using jQuery is very simple. For example, to select an element from the page, if you need to change its style, we can write like this:

$('button').click(function(){  
  $(this).hide();  
});

2. React

React is a popular library maintained by Facebook and used for building web user interfaces, specifically SPAs (Single Page Applications). React builds by creating reusable components, allowing developers to build complex UI faster.

React applications often use a compositional approach to design the UI, passing data and event handlers through component properties. React also improves rendering performance through virtual DOM algorithms.

To use React, you need to use npm or yarn to install the React library and import the React module in the code, for example:

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  <h1 id="Hello-World">Hello, World!</h1>,
  document.getElementById('root')
);

3. D3.js

D3.js is a popular JavaScript library for creating dynamic and interactive data visualizations in the web browser using HTML, CSS, and SVG. It provides various visual elements such as bar charts, pie charts or line charts, etc.

With D3, developers can use a variety of data sources to draw visualizations. D3 not only has the ability to display data in charts, but also binds data into DOM elements, allowing the actual data to be connected to the visualization.

Installation of D3.js:

$ npm install d3

Usage example of D3:

import * as d3 from 'd3';

var svg = d3.select("body")
  .append("svg")
  .attr("width", 500)
  .attr("height", 500);

svg.append("circle")
  .attr("cx", 50)
  .attr("cy", 50)
  .attr("r", 20);

Conclusion

JavaScript library allows us to complete the application faster and easier Program development and improve code reusability and maintainability. There are several ways to use JavaScript libraries, such as importing library files in HTML pages, using modules and components in ES6, etc. When using a JavaScript library, you need to understand the library's API and usage, and how to apply it to your application.

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