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Expands on when to use module.exports vs. exports. This is a recurring question on mailing list and continues to confuse new devs.
192 lines
4.9 KiB
Markdown
192 lines
4.9 KiB
Markdown
# Global Objects
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<!-- type=misc -->
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These objects are available in all modules. Some of these objects aren't
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actually in the global scope but in the module scope - this will be noted.
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## global
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<!-- type=global -->
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* {Object} The global namespace object.
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In browsers, the top-level scope is the global scope. That means that in
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browsers if you're in the global scope `var something` will define a global
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variable. In Node this is different. The top-level scope is not the global
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scope; `var something` inside a Node module will be local to that module.
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## process
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<!-- type=global -->
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* {Object}
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The process object. See the [process object][] section.
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## console
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<!-- type=global -->
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* {Object}
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Used to print to stdout and stderr. See the [console][] section.
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## Class: Buffer
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<!-- type=global -->
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* {Function}
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Used to handle binary data. See the [buffer section][]
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## require()
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<!-- type=var -->
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* {Function}
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To require modules. See the [Modules][] section. `require` isn't actually a
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global but rather local to each module.
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### require.resolve()
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Use the internal `require()` machinery to look up the location of a module,
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but rather than loading the module, just return the resolved filename.
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### require.cache
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* {Object}
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Modules are cached in this object when they are required. By deleting a key
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value from this object, the next `require` will reload the module.
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### require.extensions
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Stability: 0 - Deprecated
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* {Object}
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Instruct `require` on how to handle certain file extensions.
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Process files with the extension `.sjs` as `.js`:
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require.extensions['.sjs'] = require.extensions['.js'];
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**Deprecated** In the past, this list has been used to load
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non-JavaScript modules into Node by compiling them on-demand.
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However, in practice, there are much better ways to do this, such as
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loading modules via some other Node program, or compiling them to
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JavaScript ahead of time.
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Since the Module system is locked, this feature will probably never go
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away. However, it may have subtle bugs and complexities that are best
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left untouched.
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## __filename
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<!-- type=var -->
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* {String}
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The filename of the code being executed. This is the resolved absolute path
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of this code file. For a main program this is not necessarily the same
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filename used in the command line. The value inside a module is the path
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to that module file.
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Example: running `node example.js` from `/Users/mjr`
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console.log(__filename);
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// /Users/mjr/example.js
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`__filename` isn't actually a global but rather local to each module.
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## __dirname
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<!-- type=var -->
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* {String}
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The name of the directory that the currently executing script resides in.
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Example: running `node example.js` from `/Users/mjr`
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console.log(__dirname);
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// /Users/mjr
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`__dirname` isn't actually a global but rather local to each module.
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## module
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<!-- type=var -->
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* {Object}
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A reference to the current module. In particular
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`module.exports` is used for defining what a module exports and makes
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available through `require()`.
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`module` isn't actually a global but rather local to each module.
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See the [module system documentation][] for more information.
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## exports
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<!-- type=var -->
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A reference to the `module.exports` that is shorter to type.
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See [module system documentation][] for details on when to use `exports` and
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when to use `module.exports`.
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`exports` isn't actually a global but rather local to each module.
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See the [module system documentation][] for more information.
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See the [module section][] for more information.
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## setTimeout(cb, ms)
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Run callback `cb` after *at least* `ms` milliseconds. The actual delay depends
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on external factors like OS timer granularity and system load.
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The timeout must be in the range of 1-2,147,483,647 inclusive. If the value is
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outside that range, it's changed to 1 millisecond. Broadly speaking, a timer
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cannot span more than 24.8 days.
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Returns an opaque value that represents the timer.
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## clearTimeout(t)
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Stop a timer that was previously created with `setTimeout()`. The callback will
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not execute.
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## setInterval(cb, ms)
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Run callback `cb` repeatedly every `ms` milliseconds. Note that the actual
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interval may vary, depending on external factors like OS timer granularity and
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system load. It's never less than `ms` but it may be longer.
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The interval must be in the range of 1-2,147,483,647 inclusive. If the value is
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outside that range, it's changed to 1 millisecond. Broadly speaking, a timer
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cannot span more than 24.8 days.
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Returns an opaque value that represents the timer.
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## clearInterval(t)
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Stop a timer that was previously created with `setInterval()`. The callback
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will not execute.
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<!--type=global-->
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The timer functions are global variables. See the [timers][] section.
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[buffer section]: buffer.html
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[module section]: modules.html
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[module system documentation]: modules.html
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[Modules]: modules.html#modules_modules
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[process object]: process.html#process_process
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[console]: console.html
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[timers]: timers.html
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