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Understand the global object in nodejs and see the difference between it and the global object in the browser

青灯夜游forward: 2021-12-03 19:00:262318browse

This article will take you to understand the global objects in node, and introduce the difference between nodejs global objects and global objects in the browser. I hope it will be helpful to everyone!

In Node.js, a .js file is a complete scope (module, module). Therefore, variables declared with var are only valid in the current .js file, not globally. The global global object is independent of all .js (module, module).

The top-level global object in the browser is window, and variables declared by var are bound to the window object by default

1. Definition of global objects

Concept: Objects that can be accessed anywhere in the program are called global objects. Properties of objects are called global variables.

2. Summary of global variables in NodeJS

Here we summarize what are our commonly used global variables in nodejs

2.1 Buffer class

Buffer, we can also call it a "buffer", its function is to open up a piece of memory in the memory Area used to store binary data.

2.2 __dirname

__dirname, returns the folder where the current module file is located after parsing The absolute path to (directory).

Please remember that __dirname is not a true global variable.

2.3 __filename

##__filename, returns the current module file The parsed absolute path.

Please remember that __filename is not really a global variable.

2.4 module##Please remember that module is not a true global variable.

2.5 require()Please remember that require() is not really global variables.

2.6 exportsRemember, exports are not really global variables.

2.7 setImmediate and clearImmediate

2.8 setTimeout and clearTimeout

2.9 setInterval and clearInterval 

2.10 console is used to print to standard output and standard error

##2.11

processprocess

object provided Information about the current Node.js process and control it.

2.12

URLURL

is used for URL processing and Parsing Utilities

2.13

events##events module is Node's answer to "publish/ Implementation of the "subscribe" model (publish/subscribe). One object passes messages to another object through this module. This module provides a constructor through the EventEmitter property.

3. globalThis

3.1 What is globalThis?

The JS language is increasingly used in a variety of environments. In addition to the most common browsers, it can run on servers, smartphones, and even robot hardware. Each environment has its own object model and provides different syntax to access global objects. For example, in a web browser, global objects can be accessed through window, self, or frames. However, in Node.js, these properties do not exist and global must be used instead.

globalThis aims to consolidate the increasingly fragmented methods of accessing global objects by defining a standard global property. The proposal was incorporated into the ES2020 standard. All popular browsers, including Chrome 71, Firefox 65 and Safari 12.1, already support this feature. You can also use it in Node.js 12.

For more node-related knowledge, please visit: nodejs tutorial! !

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Understand the global object in nodejs and see the difference between it and the global object in the browser

1. Definition of global objects

2. Summary of global variables in NodeJS

3.1 What is globalThis?

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