Specific use of node.js global variables

Global Object

All modules can be called

1. global: represents the global environment of Node, similar to the window object in the browser.
2. process: points to Node's built-in process module, allowing developers to interact with the current process.
3. For example, if you directly enter node in DOS or terminal window, you will enter the NODE command line mode (REPL environment). To exit, enter process.exit();
4. console: points to the built-in console module of Node, which provides standard input and standard output functions in the command line environment.

Global Functions

Timer functions: There are 4 timer functions: setTimeout(), clearTimeout(), setInterval(), clearInterval().

require: used to load modules.

It was often seen in King Qi's house and heard several times in Cui Jiu's hall.

Global variables

• _filename: points to the name of the script currently running.
• _dirname: points to the directory where the currently running script is located.

Quasi-global variables

The local variables inside the module point to different objects depending on the module, but they are applicable to all modules and can be regarded as pseudo-global variables, mainly module, module.exports, exports, etc.

The module variable refers to the current module. The module.exports variable represents the interface exported by the current module. When other files load the module, they actually read the module.exports variable.

• module.id The module identifier, usually the module's file name.
• module.filename The filename of the module.
• module.loaded returns a boolean value indicating whether the module has finished loading.
• module.parent returns the module that uses this module.
• module.children returns an array of other modules that this module uses.
  

Global sample code

// Include the full path of the file name console.log(__filename);
// The path to the file (excluding the file name)
console.log(__dirname);

// Timing function, usage is similar to the timing function in the browser var timer = setTimeout(function(){
    console.log(123);
},1000);

setTimeout(function(){
    clearTimeout(timer);
},2000);

// There is no window object in Node.js, but there is a similar object global, which can be omitted when accessing global members
global.console.log(123456);

// argv is an array. By default, the first two items are: the path of the Node.js environment; the full path of the currently executed js file // Starting from the third parameter, it represents the command line parameters console.log(process.argv);
// Print the current system architecture (64-bit or 32-bit)
console.log(process.arch);

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