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    permalinks NPM version NPM monthly downloads NPM total downloads Linux Build Status

    Easily add powerful permalink or URL routing/URL rewriting capablities to any node.js project. Can be used in static site generators, build systems, web applications or anywhere you need to do path or URL transformation.

    Please consider following this project's author, Jon Schlinkert, and consider starring the project to show your ❤️ and support.

    (TOC generated by verb using markdown-toc)


    Install with npm:

    $ npm install --save permalinks


    Add permalinks support to any JavaScript project using node's require() system with the following line of code:

    const permalink = require('permalinks');

    (The main export is a function that automatically creates an instance of Permalinks and calls the permalinks.formt() method. As an alternative, if you need to access any internal methods, the API documentation shows how to create an instance of Permalinks.)


    permalink(structure, file[, options]);


    • structure: {string} (required) A kind of template that determines what a permalink will look like when it's rendered.
    • file: {string|object} (required) Locals, or a file object or path (the file associated with the permalink).
    • locals: {object} (optional) Additional data to use for resolving placeholder values in the structure


    console.log(permalink('/:area/:slug/index.html', {area: 'blog', slug: 'idiomatic-permalinks'}));
    //=> '/blog/idiomatic-permalinks/index.html'
    console.log(permalinks('/blog/:stem/index.html', 'src/about.hbs'));
    //=> '/blog/about/index.html'
    console.log(permalinks('/archives/:stem-:num.html', 'src/foo.hbs', {num: 21}));
    //=> '/archives/foo-21.html'



    Create an instance of Permalinks with the given options


    • options {Options|String}


    const Permalinks = require('permalinks').Permalinks;
    const permalinks = new Permalinks();
    console.log(permalinks.format(':stem/index.html'), {path: 'src/about.hbs'});
    //=> 'about/index.html'


    Uses parse-filepath to parse the file.path on the given file object. This method is called by the format method, but you can use it directly and pass the results as locals (the last argument) to the .format method if you need to override or modify any path segments.


    • file {Object}
    • returns {Object}


    console.log(permalinks.parse({path: 'foo/bar/'}));
    // { root: '',
    //   dir: 'foo/bar',
    //   base: '',
    //   ext: '.md',
    //   name: 'baz',
    //   extname: '.md',
    //   basename: '',
    //   dirname: 'foo/bar',
    //   stem: 'baz',
    //   path: 'foo/bar/',
    //   absolute: [Getter/Setter],
    //   isAbsolute: [Getter/Setter] }


    Generate a permalink by replacing :prop placeholders in the specified structure with data from the given file and locals.


    • structure {String}: Permalink structure or the name of a registered preset.
    • file {Object|String}: File object or file path string.
    • locals {Object}: Any additional data to use for resolving placeholders.
    • returns {String}


    const fp = permalinks.format('blog/:stem/index.html', {path: 'src/about.hbs'});
    //=> 'blog/about/index.html'


    Define a permalink preset with the given name and structure.


    • name {String}: If only the name is passed,
    • structure {String}
    • returns {Object}: Returns the Permalinks instance for chaining


    permalinks.preset('blog', 'blog/:stem/index.html');
    const url = permalinks.format('blog', {path: 'src/about.hbs'});
    //=> 'blog/about/index.html'


    Define permalink helper name with the given fn. Helpers work like any other variable on the context, but they can optionally take any number of arguments and can be nested to build up the resulting string.


    • name {String}: Helper name
    • fn {Function}
    • returns {Object}: Returns the Permalink instance for chaining.


    permalinks.helper('date', function(file, format) {
      return moment(;
    const structure1 = ':date(file, "YYYY/MM/DD")/:stem/index.html';
    const file1 = permalinks.format(structure1, {
      data: {date: '2017-01-01'},
      path: 'src/about.tmpl'
    const structure2 = ':name(upper(stem))/index.html';
    const file2 = permalinks.format(structure2, {
      data: {date: '2017-01-01'},
      path: 'src/about.tmpl'
    //=> '2017/01/01/about/index.html'
    //=> '2017/01/01/about/index.html'


    Add a function for calculating the context at render time. Any number of context functions may be used, and they are called in the order in which they are defined.


    • fn {Function}: Function that takes the file being rendered and the context as arguments. The permalinks instance is exposed as this inside the function.
    • returns {Object}: Returns the instance for chaining.


    permalinks.context(function(file, context) { = { title: 'My Blog' };
    permalinks.helper('title', function() {
      return ||;


    Normalize the given file to be a vinyl file object.


    • file {String|Object}: If file is a string, it will be converted to the file.path on a file object.
    • file {Object}
    • options {Object}
    • returns {Object}: Returns the normalize vinyl file.


    const file = permalinks.normalizeFile('foo.hbs');
    //=> '<File "foo.hbs">'


    What is a permalink?

    The word "permalink" is a portmanteau for "permanent link". A permalink is a URL to a page, post or resource on your site that is intended to stay the same as long as the site exists.

    Most blogging platforms and static site generators offer some level of support or plugins for generating permalinks. To users surfing your site, a permalink represents an entire "absolute" URL, such as However, you will probably only need to generate the relative path portion of the URL: /foo/index.html.

    How are permalinks created?

    A permalink is created by replacing placeholder values in a [permalink structure] with actual data. This data is provided by the user in the form of locals, and/or created by parsing the [file path]:

    // given this structure
    // and this data
    { slug: 'my-first-blog-post' }
    // the resulting (relative part of the) permalink would be

    This is covered in greater detail in the following documentation.


    A permalink structure is a template that determines how your permalink should look after it's rendered.

    Structures may contain literal strings, and/or placeholder strings like :name, which will be replaced with actual data when the format method is called.


    Given a file named, we can change the aesthetics or semantics of the resulting permalink simply by changing the structure. For example:

    //=> blog/10-powerful-seo-tips/
    //=> blog/10-powerful-seo-tips.html
    //=> blog/10-powerful-seo-tips/index.html

    With a bit more information, provided as locals or from the file itself (such as, which commonly holds parsed front-matter data), we can get much more creative:

    For example, if was defined as more-powerful-seo-tips, we might use it like this:

    //=> blog/more-powerful-seo-tips/index.html

    We can get even more creative using helpers. We might, for example:

    • create a helper that parses a date from front-matter, such as 2017-01-02, into year, month and day
    • slugifies a title, like "Foo Bar Baz", to be dash-separated and all lower-case
    • adds the index of a file from an array of files
    '/blog/:date(, "YYYY/MM/DD")/index.html'
    //=> blog/:slugify(data.title)/index.html
    //=> blog/:slugify(data.title)/index.html
    //=> archives/23.html

    Your creativity is the only limitation!

    Alternative syntax

    Permalinks uses handlebars to resolve templates, which means that you can also/alternatively use handlebar's native mustache syntax for defining permalink structures:


    Why handlebars?

    There are a few reasons we decided to use Handlebars over parsing/rendering the :params internally:

    • Excellent context handling and resolution of variables. We have a lot of experience with templating, parsing and rendering. Most libraries choose the "minimalist" route for resolving :prop strings because of all the edge cases that crop up with more advanced features, and it's fast. With Handlebars, we compromise very slightly on speed (although it's still very fast) in exchange for power and reliability.
    • Helpers! You can use helpers to modify any of the variables in your permalink structure. You can even register helpers from great libraries like template-helpers or handlebars-helpers
    • Error handling: handlebars provides great error handling, but we especially like that handlebars allows us to choose what should happen when a missing helper is identified. We use that feature to detect dates and other similar patterns that might need to be parsed before calling other helpers (for example, let's say you define :month/:year/:day, but none of those variables exist. handlebars will call the helperMissing helper for each param, which gives you the opportunity to, for example, parse into an object with those properties, and return the values instead of throwing an error)
    • Other advanced handlebars features, like subexpressions and object paths (

    Example using subexpressions

    '/blog/{{lower (slugify data.title)}}/index.html'
    // or 
    '/blog/:lower((slugify data.title))/index.html'

    Note that :lower( is effectively converted to {{lower, thus only the outermost subexpression will result in double parentheses. This is easier to see in the following example, which has two nested subexpressions:

    '/blog/:foo((bar (baz "qux")))/index.html'

    If the :param syntax seems confusing, feel free to stick with the handlebars syntax.


    Type: {String|Object} (optional if locals is passed)

    If a file object or string is passed, it will be parsed using node's path.parse() method, and merged with locals to create the context for resolving :props in the structure.

    permalinks(structure, file, locals);
    //                     ↑

    File handling

    Files may be defined as a string or an object. If defined as a string, the filepath will be converted to an object and set on the file.path property.

    In other words 'a/b/' becomes { path: 'a/b/' }.


    Type: (optional if file is passed)

    Additional data to use for resolving :props in the structure

    permalinks(structure, file, locals);
    //                            ↑


    The "context" is an in-memory object that is used to resolve placeholders in permalink structures.

    The context object is created dynamically before rendering each permalinks, by merging the following objects:


    If a locals object is passed as the last argument, it will be merged onto the context to be used for resolving placeholders in the permalink structure.

    console.log(permalinks('/blog/:name/index.:ext', 'src/about.hbs', {ext: '.html'}));
    //=> '/blog/about/index.html'
    console.log(permalinks(':category/:name/index.html', 'src/about.hbs', {category: 'blog'}));
    //=> 'blog/about/index.html'

    Type: object

    Default: undefined

    Populate the object with additional data to use for a specific file when rendering a permalink structure.

    Type: object

    Default: undefined

    Provide additional data to use when rendering permalinks for all files.

    File path properties

    Values on the provided file object are merged onto the root of the context and are used to resolve placeholders in the permalink structure. File values can be overridden by locals or helpers.

    A file does not need to be passed, but if a file is provided with at least a file.path property, the path will be parsed to provide as many of the following variables on the context as possible.

    variable description
    file.base Gets and sets base directory. Used for created relative paths. When null or undefined, it simply proxies the file.cwd property. Will always be normalized and have trailing separators removed. Throws when set to any value other than non-empty strings or null/undefined.
    file.path Gets and sets the absolute pathname string or undefined. This value is always normalized and trailing separators are removed. Throws when set to any value other than a string.
    file.relative Gets the result of path.relative(file.base, file.path). This is a getter and will throw if set or when file.path has not already been set.
    file.dirname Gets and sets the dirname of file.path. Will always be normalized and have trailing separators removed. Throws when file.dirname is not exlicitly defined and/or file.path is not set.
    file.basename Gets and sets the basename of file.path. Throws when file.basename is not exlicitly defined and/or file.path is not set.
    file.stem Gets and sets stem (filename without suffix) of file.path. Throws when file.stem is not exlicitly defined and/or file.path is not set. Alias for file.stem.
    file.extname Gets and sets extname property of file.path.
    file.ext Alias for file.extname.


    │                     file.path                    │
    │      file.dirname     │        file.basename     │
    │                       ├──────────┬─────────────┤
    │                       │ │              │
    │                       │ file.stem │ file.extname │
    " /home/user/foo/src    /   about        .tmpl      "

    A file.relative value can only be calculated if both file.base and file.path exist:

    │                     file.path                    │
    │      file.base        │        file.relative     │


    Easily store and re-use permalink structures.

    (If you're familiar with the popular blogging platform, WordPress, you might also be familiar with the built-in "Permalinks Settings" that WordPress offers. This feature attempts to replicate and improve on that functionality.)


    Create a pretty preset for automatically formatting URLs, where the file.stem of a blog post is used as the folder name, followed by /index.html:

    const permalinks = new Permalinks();
    permalinks.preset('pretty', 'blog/:slugify(title)/index.html');
    console.log(permalinks.format(':pretty', 'foo/bar/baz.hbs', {title: 'Post One'}));
    //=> 'blog/post-one/index.html'
    console.log(permalinks.format(':pretty', 'foo/bar/qux.hbs', {title: 'Post Two'}));
    //=> 'blog/post-two/index.html'


    Helper functions can be used to resolve placeholders in permalink structures. For example:

    // register a helper function
    permalinks.helper('foo', function() {
      // return the value to use to replace "foo"
      return this.file.stem;
    const url = permalinks.format('/:foo', {path: 'about.hbs'});
    //=> '/about'
    Helper example

    Use a date helper to dynamically generate paths based on the date defined in YAML front matter of a file.

    var moment = require('moment');
    var Permalinks = require('permalinks');
    var permalinks = new Permalinks();
    var file = {
      path: 'src/about.hbs',
      data: {
        date: '2017-02-14'
    // "" is merged onto "this.context" 
    permalinks.helper('date', function(format) {
      return moment( || 'YYYY/MM/DD');
    console.log(permalinks.format(':date/:stem/index.html', file));
    //=> '2017/02/14/about/index.html'

    Helpers can also take arguments:

    console.log(permalinks.format(':date("YYYY")/:stem/index.html', file));
    //=> '2017/about/index.html'

    See the helper unit tests for more examples.

    file helper

    A special built-in file helper is called on every file and then removed from the context before rendering.

    permalinks.helper('file', function(file, data, locals) {
      // do stuff with file, data and locals

    You can override this helper to modify the context or set properties on files before generating permalinks.

    `file` helper example

    Use the file helper to increment a value for pagination or something similar:

    var file = new File({path: 'foo/bar/baz.hbs'});
    var permalinks = new Permalinks();
    var count = 0;
    permalinks.helper('file', function(file, data, locals) {
      data.num = ++count;
    console.log(permalinks.format(':num-:basename', file));
    //=> '1-baz.hbs'
    console.log(permalinks.format(':num-:basename', file));
    //=> '2-baz.hbs'
    console.log(permalinks.format(':num-:basename', file));
    //=> '3-baz.hbs'
    //=> 3

    Additional resources

    Here is some reading material if you're interested in learning more about permalinks.



    Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

    Running Tests

    Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:

    $ npm install && npm test
    Building docs

    (This project's is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the readme template.)

    To generate the readme, run the following command:

    $ npm install -g verbose/verb#dev verb-generate-readme && verb

    Related projects

    You might also be interested in these projects:

    • handlebars: Handlebars provides the power necessary to let you build semantic templates effectively with no frustration | homepage
    • parse-filepath: Pollyfill for node.js path.parse, parses a filepath into an object. | homepage
    • vinyl: Virtual file format. | homepage


    Jon Schlinkert


    Copyright © 2018, Jon Schlinkert. Released under the MIT License.

    This file was generated by verb-generate-readme, v0.6.0, on January 11, 2018.


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