Detailed explanation of the basics of Node.js global objects

This article mainly introduces the relevant information of the global object in the Node.js basic tutorial. The global object in Node.js is global. All global variables (except global itself) are attributes of the global object. Friends in need You can refer to the following

Node.js basic tutorial global object

• In browser JavaScript, usually window is the global object.

• The global object in Node.js is global, and all global variables (except global itself) are properties of the global object.

• global's most fundamental role is to serve as the host of global variables.

• Note: Always use var to define variables to avoid introducing global variables, because global variables will pollute the namespace and increase the risk of code coupling.
  

#__filename script absolute path

represents the file name of the currently executing script. It will output the absolute path of the file location, and may not be the same as the file name specified by the command line parameter. If in a module, the returned value is the path to the module file.

console.log(__filename);
// C:\Users\admin\main.js

__dirname The directory where the script is located

indicates the directory where the currently executing script is located.

console.log(__dirname);
// C:\Users\admin

setTimeout(cb, ms) Execute function cb once

The global function is executed after the specified number of milliseconds (ms) Specify function(cb).

setTimeout() only executes the specified function once.

Returns a handle value representing the timer.

function printHello(){
  console.log( "Hello, World!");
}
// 两秒后执行以上函数
setTimeout(printHello, 2000);

clearTimeout(t) Stop function t

clearTimeout(t) The global function is used to stop a function that was previously passed through setTimeout() Created timer. The parameter t is the timer created through the setTimeout() function.

function printHello(){
  console.log( "Hello, World!");
}
// 两秒后执行以上函数
var t = setTimeout(printHello, 2000);
clearTimeout(t)

setInterval(cb, ms) Keep calling function cb

setInterval(cb, ms) 全局函数在指定的毫秒(ms)数后执行指定函数(cb)。
返回一个代表定时器的句柄值。可以使用 clearInterval(t) 函数来清除定时器。
setInterval() 方法会不停地调用函数，直到 clearInterval() 被调用或窗口被关闭。
function printHello(){
  console.log( "Hello, World!");
}
// 两秒后执行以上函数
setInterval(printHello, 2000);

process A simple interface with the operating system

process is a global variable, which is a property of the global object.

It is an object used to describe the current Node.js process status and provides a simple interface with the operating system. Usually when you write a local command line program, you have to deal with it.

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