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How to use the path module?

by Mr. Nico Reed nicoreed on

The path module contains several helper functions to help make path manipulation easier.

The first function worth mentioning is path.normalize. This function takes a path (in the form of a string) and strips it of duplicate slashes and normalizes directory abbreviations, like '.' for 'this directory' and '..' for 'one level up'. For example:

> var path = require('path');
> path.normalize('/a/.///b/d/../c/')
'/a/b/c/'

A closely related function to normalize is join. This function takes a variable number of arguments, joins them together, and normalizes the path.

> var path = require('path');
> path.join('/a/.', './//b/', 'd/../c/')
'/a/b/c'

A possible use of join is to manipulate paths when serving urls:

> var path = require('path');
> var url = '/index.html';
> path.join(process.cwd(), 'static', url);
'/home/nico/static/index.html'

There are three functions which are used to extract the various parts of the path name: basename, extname, and dirname. - basename returns the last portion of the path passed in. - extname returns the extension of the last portion. Generally for directories, extname just returns ''. - Finally, dirname returns everything that basename does not return. For example:

> var path = require('path')
> var a = '/a/b/c.html'
> path.basename(a)
'c.html'
> path.extname(a)
'.html'
> path.dirname(a)
'/a/b'

Note that basename has an optional second parameter that will strip out the extension if you pass the correct extension.

> var path = require('path')
> var a = '/a/b/c.html'
> path.basename(a, path.extname(a))
'c'

Lastly, the path module provides methods to check whether or not a given path exists: exists and existsSync They both take the path of a file for the first parameter.

exists takes a callback as its second parameter, to which is returned a boolean representing the existance of the file.

existsSync, on the other hand, checks the given path synchronously, returning the boolean directly. In Node.js, you will typically want to use the asynchronous functions for most file system I/O - the synchronous versions will block your entire process until they finish.

Blocking isn't always a bad thing. Checking the existence of a vital configuration file synchronously makes sense, for example - it doesn't matter much if your process is blocking for something it can't run without! Conversely, though, in a busy HTTP server, any per-request file I/O MUST be asynchronous, or else you'll be responding to requests one by one. See the article on asynchronous operations for more details.

    > var path = require('path')
    > path.exists('/etc', function(exists){console.log("Does the file exist?", exists)})
    > Does the file exist? true

    > path.existsSync('/etc')
    true