Let's talk about built-in objects that are not part of javascript

JavaScript is a powerful scripting language that has become one of the preferred languages ​​for web development due to its flexibility and scalability. In JavaScript, there are many built-in objects that can help developers perform various operations, such as arrays, dates, strings, etc. However, there are also some things that are not built-in objects in JavaScript, and this article will discuss these things that are not built-in objects.

1. BOM (Browser Object Model)

BOM is a set of APIs provided by the browser that provide access to the browser window itself and all objects that interact with it. Although JavaScript itself has no built-in objects to handle browser windows or other browser-specific functions, the BOM provides interfaces for these functions, such as window objects, navigator objects, location objects, etc.

BOMs cannot be counted as JavaScript built-in objects because they are not actually associated with the JavaScript language, but with the browser. Different browsers may provide different versions of BOM interfaces, so when writing cross-browser JavaScript code, you need to handle BOM differences carefully.

2. DOM (Document Object Model)

DOM is a standard programming interface used to represent HTML documents. It represents HTML documents as a tree structure and allows JavaScript code Access and modify the content, structure, and style of documents. Although DOM is often used in JavaScript, it cannot be regarded as a built-in JavaScript object.

The implementation of DOM is provided by browser manufacturers. Like BOM, it is not part of JavaScript itself, but is extended by JavaScript. Although not completely consistent, most major browsers follow the specifications of the W3C DOM standard, so writing code across browsers only needs to deal with a relatively small subset.

3. XMLHttpRequest

XMLHttpRequest is an API for sending and receiving data through HTTP. It can realize asynchronous data transmission and is the core of Ajax (Asynchronous JavaScript and XML) programming. . Although XMLHttpRequest is often used in JavaScript, it is not a built-in JavaScript object.

XMLHttpRequest became a W3C standard in 2006. Its implementation is provided by the browser and is not essentially related to JavaScript. Although there are now some new APIs, such as Fetch API, that can replace XMLHttpRequest for data transfer, it is still widely used.

4. JSON (JavaScript Object Notation)

JSON is a lightweight format for data exchange, and it is widely used in web applications. JSON syntax is a subset of JavaScript objects that uses a text format rather than a binary format, which can simplify the development of web applications.

Although JSON syntax is similar to JavaScript object syntax, JSON itself is not a JavaScript object. JSON is a JavaScript-independent format that can be used in any programming language. In JavaScript, you can convert objects to and from JSON format through the JSON.parse() and JSON.stringify() methods.

Summary

This article introduces some content that is not a built-in object of JavaScript, including BOM, DOM, XMLHttpRequest and JSON. Although these contents have not directly become part of the JavaScript core language, they are often widely used in actual web development. Although these extensions, which are not part of the core JavaScript language, can greatly extend the functionality of JavaScript code, their differences and limitations still need to be carefully managed.

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