Nodejs中的Global object全局对象

朴灿烈づ我的快乐病毒、 2022-06-07 02:42 216阅读 0赞

# Global Objects全局对象 #

These objects are available in all modules. Some of these objects aren't actually in the global scope but in the module scope - this will be noted.

这么对象在所有的模块中可用，那些不在全局范围的对象而在模块范围的对象会被注明的。

## global[\#][Link 1] ##

*  \{Object\} The global namespace object.全局命名空间对象

In browsers, the top-level scope is the global scope. That means that in browsers if you're in the global scope `var something` will define a global variable. In Node this is different. The top-level scope is not the global scope; `var something` inside a Node module will be local to that module.

在游览器中，最上层区域就是全局区域。意思就是在全局区域定义的变量就是全局变量。但是在Nodejs中是不同的，最上层区域不是全局区域，

在某一个node模块中定义的变量只能是属于该模块

## process[\#][Link 2] ##

*  \{Object\}

The process object. See the [ process object][process object] section.

The `process` object is a global object and can be accessed from anywhere. It is an instance of [EventEmitter][].

process对应是个全局变量，可以再任何地方引用它，它是一个EventEmiitter的实例

## console[\#][Link 3] ##

*  \{Object\}

Used to print to stdout and stderr. See the [ stdio][stdio] section.

用于打印标准输出和标准错误

## Class: Buffer[\#][Link 4] ##

*  \{Function\}

Used to handle binary data. See the [ buffer section][buffer section]

用于处理字节数据，这样因为，Node.js处理TCP Stream和文件时使用的八进制流，而客服端的JavaScript是对binary data处理并不友好

在node.js中就专门创建了Buffer类来处理binary data。

## require()[\#][Link 5] ##

*  \{Function\}

To require modules. See the [ Modules][Modules] section.  `require` isn't actually a global but rather local to each module.

用于将一个模块加载到另一个模块中，但require事实上并不是全局的，而是每一模块中的全局方法。

### require.resolve()[\#][Link 6] ###

Use the internal `require()` machinery to look up the location of a module, but rather than loading the module, just return the resolved filename.

使用内部require()工具找到某个module的位置，而不是上传该module,最终返回的是一个解析后的文件名

### require.cache[\#][Link 7] ###

*  Object

Modules are cached in this object when they are required. By deleting a key value from this object, the next `require` will reload the module.

在模块被请求时就被缓存到了该对象中。从该对象中删除键值，再一次用require该模块又将缓存它到该对象中。

### require.extensions[\#][Link 8] ###

*  Array

Instruct `require` on how to handle certain file extensions.

Process files with the extension `.sjs` as `.js`:

require.extensions['.sjs'] = require.extensions['.js'];

Write your own extension handler:

require.extensions['.sjs'] = function(module, filename) { 
      var content = fs.readFileSync(filename, 'utf8');
      // Parse the file content and give to module.exports
      module.exports = content;
    };

require扩展方法

## \_\_filename[\#][Link 9] ##

*  \{String\}

The filename of the code being executed.  This is the resolved absolute path of this code file.  For a main program this is not necessarily the same filename used in the command line.  The value inside a module is the path to that module file.

Example: running `node example.js` from `/Users/mjr`

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

`__filename` isn't actually a global but rather local to each module.

当前文件的名称

## \_\_dirname[\#][Link 10] ##

*  \{String\}

The name of the directory that the currently executing script resides in.

Example: running `node example.js` from `/Users/mjr`

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

`__dirname` isn't actually a global but rather local to each module.

当前文件所在的目录

## module[\#][Link 11] ##

*  \{Object\}

A reference to the current module. In particular`module.exports` is the same as the `exports` object.`module` isn't actually a global but rather local to each module.

See the [module system documentation][] for more information.

## exports[\#][Link 12] ##

An object which is shared between all instances of the current module and made accessible through `require()`.`exports` is the same as the `module.exports` object.`exports` isn't actually a global but rather local to each module.

See the [module system documentation][] for more information.

See the [module section][module system documentation] for more information.

下面的定时处理方法，就不多说了，和JavaScript中的一样

## setTimeout(cb, ms)[\#][Link 13] ##

Run callback `cb` after *at least* `ms` milliseconds. The actual delay depends on external factors like OS timer granularity and system load.

The timeout must be in the range of 1-2,147,483,647 inclusive. If the value is outside that range, it's changed to 1 millisecond. Broadly speaking, a timer cannot span more than 24.8 days.

Returns an opaque value that represents the timer.

## clearTimeout(t)[\#][Link 14] ##

Stop a timer that was previously created with `setTimeout()`. The callback will not execute.

## setInterval(cb, ms)[\#][Link 15] ##

Run callback `cb` repeatedly every `ms` milliseconds. Note that the actual interval may vary, depending on external factors like OS timer granularity and system load. It's never less than `ms` but it may be longer.

The interval must be in the range of 1-2,147,483,647 inclusive. If the value is outside that range, it's changed to 1 millisecond. Broadly speaking, a timer cannot span more than 24.8 days.

Returns an opaque value that represents the timer.

## clearInterval(t)[\#][Link 16] ##

Stop a timer that was previously created with `setInterval()`. The callback will not execute.

The timer functions are global variables. See the [ timers][timers] section.

[Link 1]: http://nodejs.org/api/globals.html#globals_global
[Link 2]: http://nodejs.org/api/globals.html#globals_process
[process object]: http://nodejs.org/api/process.html#process_process
[EventEmitter]: http://nodejs.org/api/events.html#events_class_events_eventemitter
[Link 3]: http://nodejs.org/api/globals.html#globals_console
[stdio]: http://nodejs.org/api/stdio.html
[Link 4]: http://nodejs.org/api/globals.html#globals_class_buffer
[buffer section]: http://nodejs.org/api/buffer.html
[Link 5]: http://nodejs.org/api/globals.html#globals_require
[Modules]: http://nodejs.org/api/modules.html#modules_modules
[Link 6]: http://nodejs.org/api/globals.html#globals_require_resolve
[Link 7]: http://nodejs.org/api/globals.html#globals_require_cache
[Link 8]: http://nodejs.org/api/globals.html#globals_require_extensions
[Link 9]: http://nodejs.org/api/globals.html#globals_filename
[Link 10]: http://nodejs.org/api/globals.html#globals_dirname
[Link 11]: http://nodejs.org/api/globals.html#globals_module
[module system documentation]: http://nodejs.org/api/modules.html
[Link 12]: http://nodejs.org/api/globals.html#globals_exports
[Link 13]: http://nodejs.org/api/globals.html#globals_settimeout_cb_ms
[Link 14]: http://nodejs.org/api/globals.html#globals_cleartimeout_t
[Link 15]: http://nodejs.org/api/globals.html#globals_setinterval_cb_ms
[Link 16]: http://nodejs.org/api/globals.html#globals_clearinterval_t
[timers]: http://nodejs.org/api/timers.html