What is the global object of node?

In node, the global object is an object that can be used directly without reference. It can be divided into: 1. Global objects used for module packaging; 2. Process objects; 3. Console module; 4 , EventLoop related API; 5. Buffer object; 6. global.

The operating environment of this tutorial: windows10 system, nodejs version 12.19.0, Dell G3 computer.

What is the global object of node

The global object is an object that can be used directly without a reference. It should be noted that the global object is different from the global keyword.

nodejs global objects are divided into the following categories:

1. Global objects used for module packaging

(1 ) exports

(2) module

(3) require

(4)__filename: current file name

(5)__dirname: current file directory

2. Process object

3. Console module

4. EventLoop related api

(1)setImmediate

(2)setInterval

(3)setTimeout

(4)Related clear

5. Buffer object

6.global

All global variables (except global itself) are attributes of the global object

Examples are as follows:

Class:Buffer

Can handle binary and non-Unicode encoded data

The original data is stored in the Buffer class instantiation. Buffer is similar to an integer array, and memory is allocated to it in the V8 heap original storage space

Once a Buffer instance is created, the size cannot be changed

process

Process object, provides information and control about the current process

Included in the process of executing the node program, if parameters need to be passed, we want to obtain this parameter need to be in the process built-in object

Start the process:

 node index.js 参数1 参数2 参数3

The index.js file is as follows:

process.argv.forEach((val, index) => {
  console.log(`${index}: ${val}`);});

The output is as follows:

/usr/local/bin/node/Users/mjr/work/node/process-args.js
参数1参数2参数3

In addition, it also includes some other information such as version and operating system Wait

console

Used to print stdout and stderr

The most commonly used way to input content: console .log

console.log("hello");

Clear the console: console.clear

console.clear

Print the call stack of the function: console.trace

function test() {
    demo();}function demo() {
    foo();}function foo() {
    console.trace();}test();

clearInterval, setInterval

Set timer and clear timer

setInterval(callback, delay[, ...args])

callback is executed repeatedly every delay milliseconds

clearInterval is the corresponding method for canceling the timer

clearTimeout, setTimeout

Set delayer and clear delayer

setTimeout(callback,delay[,...args])

callback is executed once after delay milliseconds

clearTimeout is the method corresponding to canceling the delayer

global

Global namespace object, the process, console, setTimeout, etc. mentioned on the wall are all placed in global中

console.log(process === global.process) // true

Module-level global objects

These global objects are variables in the module, but each module has them. They look like global variables, like in It cannot be used in command interaction, including:

• __dirname
• __filename
• exports
• module
• require

__dirname

Get the path of the current file, excluding the following file name

Run node example.js from /Users/mjr:

console.log(__dirname);// 打印: /Users/mjr

__filename

Get the path and file name of the current file, including the subsequent file name

Run node example from /Users/mjr. js:

console.log(__filename);// 打印: /Users/mjr/example.js

exports

module.exports is used to specify the content exported by a module, that is, the content that can be accessed through require()

exports.name = name;exports.age = age;exports.sayHello = sayHello;

module

The reference to the current module is used to specify the content exported by a module through module.exports, that is, the content that can be accessed through require()

require

Used to import modules, JSON, or local files. Modules can be imported from node_modules.

You can use relative paths to introduce local modules or JSON files. The path will be processed according to the directory name defined by __dirname or the current working directory

Recommended learning: "nodejs video tutorial》

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