grunt-usemin
Replaces references to non-optimized scripts or stylesheets into a set of HTML files (or any templates/views).
Watch out, this task is designed for Grunt 0.4 and upwards.
Getting Started
If you haven't used grunt before, be sure to check out the Getting Started guide, as it explains how to create a gruntfile as well as install and use grunt plugins. Once you're familiar with that process, install this plugin with this command:
npm install grunt-usemin --save-dev
Tasks
usemin
exports 2 different tasks:
-
useminPrepare
prepares the configuration to transform specific construction (blocks) in the scrutinized file into a single line, targeting an optimized version of the files (e.g concatenated, uglifyjs-ed ...)
-
usemin
replaces the blocks by the file they reference, and replaces all references to assets by their revisioned version if it is found on the disk. This target modifies the files it is working on.
Usually, useminPrepare
is launched first, then the steps of the transformation flow (for example, concat
, uglify
, and cssmin
), and then, in the end usemin
is launched.
The useminPrepare task
useminPrepare
task updates the grunt configuration to apply a configured transformation flow to tagged files (i.e. blocks).
By default the transformation flow is composed of concat
and uglifyjs
for JS files, but it can be configured.
Blocks
Blocks are expressed as:
... HTML Markup, list of script / link tags.
- type: either
js
or css
- alternate search path: (optional) By default the input files are relative to the treated file. Alternate search path allows one to change that
- path: the file path of the optimized file, the target output
An example of this in completed form can be seen below:
<script src="js/app.js"></script>
<script src="js/controllers/thing-controller.js"></script>
<script src="js/models/thing-model.js"></script>
<script src="js/views/thing-view.js"></script>
Transformation flow
The transformation flow is made of sequential steps: each of the steps transform the file, and useminPrepare will modify the configuration in order for the described steps to be correctly performed.
By default the flow is: concat -> uglifyjs
.
Additionally to the flow, at the end, some postprocessors can be launched to further alter the configuration.
Let's have an example, using the default flow (we're just going to look at the steps), app
for input dir, dist
for output dir, and the following block:
<script src="js/app.js"></script>
<script src="js/controllers/thing-controller.js"></script>
<script src="js/models/thing-model.js"></script>
<script src="js/views/thing-view.js"></script>
The produced configuration will look like:
{
concat: {
'.tmp/concat/js/app.js': [
'app/js/app.js',
'app/js/controllers/thing-controller.js',
'app/js/models/thing-model.js',
'app/js/views/thing-view.js'
]
},
uglifyjs: {
'dist/js/app.js': ['.tmp/concat/js/app.js']
}
}
Directories
Internally, the task parses your HTML markup to find each of these blocks, and initializes the corresponding Grunt config for the concat / uglify tasks when type=js
, the concat / cssmin tasks when type=css
.
One doesn't need to specify a concat/uglify/cssmin configuration anymore.
It uses only one target: html
, with a list of the concerned files. For example, in your Gruntfile.js
:
By default, it will consider the directory where the looked-at file is located as the 'root' filesystem. Each relative path (for example to a javascript file) will be resolved from this path. Same goes for the absolute ones.
If you need to change the 'root' dir, use the root
option (see bellow).
'useminPrepare': {
html: 'index.html'
}
Targets can also be configured using the grunt src-dest files syntax http://gruntjs.com/configuring-tasks#files, e.g.
useminPrepare: {
foo: {
src: ['index.html', 'another.html']
},
bar: {
src: 'index.html'
}
}
Options
dest
Type: 'string'
Default: nil
Base directory where the transformed files should be output.
staging
Type: 'string'
Default: .tmp
Base directory where the temporary files should be output (e.g. concatenated files).
root
Type: 'string'
Default: nil
The root directory from which your files will be resolved.
flow
Type: 'object'
Default: { steps: { 'js': ['concat', 'uglify'], 'css': ['concat', 'cssmin']}, post: {}}
This allow you to configure the workflow, either on a per-target basis, or for all the targets.
You can change the steps
or the post-processors (post
) separately.
For example:
- to change the
js
steps
and post
for the target html
:
'useminPrepare', {
html: 'index.html',
options: {
flow: {
html: {
steps: {'js': ['uglifyjs']},
post: {}
}
}
}
}
- to change the
js
steps
and post
for all targets:
'useminPrepare', {
html: 'index.html',
options: {
flow: {
steps: {'js' : ['uglifyjs'] },
post: []
}
}
}
The given steps or post-processors may be specified as strings (for the default steps and post-processors), or as an object (for the user-defined ones).
User-defined steps and post-processors
User-defined steps and post-processors must have 2 attributes:
name
: name of the Gruntfile
attribute that holds the corresponding configcreateConfig
which is a 2 arguments function ( a context
and the treated block
)
For an example of steps/post-processors, you can have a look at concat
and uglifyjs
in the lib/config
directory of this repository.
createConfig
The createConfig
function is responsible for creating (or updating) the configuration associated to the current step/post-processor.
It takes 2 arguments ( a context
and the treated block
), and returns a configuration object.
context
The context
object represent the current context the step/post-processor is running in. As the step/post-processor is a step of a flow, it must be listed in the input files and directory it must write a configuration for, potentially the already existing configuration. It must also indicate to the other steps/post-processor which files it will output in which directory. All this information is held by the context
object.
Attributes:
inDir
: the directory where the input
file for the step/post-processors will beinFiles
: the list of input file to take care ofoutDir
: where the files created by the step/post-processors will beoutFiles
: the files that are going to be createdlast
: whether or not we're the last step of the flowoptions
: options of the Gruntfile.js
for this step (e.g. if the step is named foo
, holds configuration of the Gruntfile.js
associated to the attribute foo
)
block
The actual looked-at block, parsed an put in a structure.
Example:
The following block
',
<script src="foo.js"></script>',
<script src="bar.js"></script>',
<script src="baz.js"></script>',
'
is parsed as, and given to createConfig
as:
var block = {
type: 'js',
dest: 'scripts/site.js',
src: [
'foo.js',
'bar.js',
'baz.js'
],
raw: [
' <!-- build:js scripts/site.js -->',
' <script src="foo.js"></script>',
' <script src="bar.js"></script>',
' <script src="baz.js"></script>',
' <!-- endbuild -->'
]
};
The usemin task
The usemin
task has 2 actions:
- First it replaces all the blocks with a single "summary" line, pointing to a file creating by the transformation flow.
- Then it looks for references to assets (i.e. images, scripts, ...), and tries to replace them with their revved version if it can find one on disk
Finding assets
By default usemin
will look for a map object created by grunt-filerev, located in grunt.filerev.summary
. If it does not find it it will revert to disk lookup which is longer.
Note that by using the options.revmap
(see below), you can furnish a map object.
On directories
When usemin
tries to replace referenced assets with their revved version it has to look at a collection of directories (asset search paths): for each of the directories of this collection it will look at the below tree, and try to find the revved version.
This asset search directories collection is by default set to the location of the file that is scrutinized but can be modified (see Options below).
Example 1: file dist/html/index.html
has the following content:
<link rel="stylesheet" href="styles/main.css">
<img src="../images/test.png">
By default usemin
will look under dist/html
for revved versions of:
styles/main.css
: a revved version of main.css
will be looked at under the dist/html/styles
directory. For example a file dist/html/styles/main.1234.css
will match (although dist/html/main.1234.css
won't: the path of the referenced file is important)../images/test.png
: it basically means that a revved version of test.png
will be looked for under the dist/images
directory
Example 2: file dist/html/index.html
has the following content:
<link rel="stylesheet" href="/styles/main.css">
<img src="/images/test.png">
By default usemin
will look under dist/html
for revved versions of styles/main.css
and images/test.png
. Now let's suppose our assets are scattered in dist/assets
. By changing the asset search path list to ['dist/assets']
, the revved versions of the files will be searched for under dist/assets
(and thus, for example, dist/assets/images/test.875487.png
and dist/assets/styles/main.98090.css
) will be found.
Options
assetsDirs
Type: 'Array'
Default: Single item array set to the value of the directory where the currently looked at file is.
List of directories where we should start to look for revved version of the assets referenced in the currently looked at file.
Example:
usemin: {
html: 'build/index.html',
options: {
assetsDirs: ['foo/bar', 'bar']
}
}
patterns
Type: 'Object'
Default: Empty
Allows for user defined pattern to replace reference to files. For example, let's suppose that you want for some reason replace
all references to 'image.png'
in your Javascript files by the revved version of image.png
found bellow the directory images
.
By specifying something along the lines of:
usemin: {
js: '*.js',
options: {
assetsDirs: 'images',
patterns: {
js: [[/(image\.png)/, 'Replacing reference to image.png']]
}
}
}
So in short:
- key in pattern should match the target (e.g
js
key for the target js
) - Each pattern is an array of arrays. These arrays are composed of 4 items (last 2 are optionals):
- First one if the regexp to use. The first group is the one that is supposed to represent the file
reference to replace
- Second one is a logging string
revmap
Type: 'String'
Default: Empty
Indicate the location of a map file, as produced by grunt-rev
for example. This map file is a simple JSON file, holding an object
which attributes are the original file and associated value is the transformed file. For example:
{
"foo.png": "foo.1234.png"
}
This map will be used instead of looking for file on the disk.
On directories
The main difference to be kept in mind, regarding directories and tasks, is that for useminPrepare
, the directories needs to indicate the input,
transient and output path needed to output the right configuration for the processors pipeline,
whereas in the case of usemin
it only reflects the output paths, as all the needed assets should have
been output to the destination dir (either transformed or just copied)
useminPrepare
useminPrepare
is trying to prepare the right configuration for the pipeline of actions that are going to be
applied on the blocks (for example concatenation and uglify-cation). As such it needs to have the input
directory, temporary directories (staging) and destination directory.
The files referenced in the block are either absolute or relative (/images/foo.png
or ../../images/foo.png
).
Absolute files references are looked in a given set of search path (input), which by default is set
to the directory where the html/css file examined is located (can be overriden per block, or more
generally through root
option).
Relative files references are also looked at from location of the examined file, unless stated otherwise.
usemin
usemin
target replaces references to images, scrips, css, ... in the furnished files (html, css, ...).
These references may be either absolute (i.e. /images/foo.png
) or relative (i.e. image/foo.png
or ../images/foo.png
).
When the reference is absolute a set of asset search paths should be looked at under the
destination directory (for example, using the previous example, and searchpath
equal to ['assets']
, usemin
would try to find either a revved version of the image
of the image bellow the assets
directory: for example dest/assets/images/foo.1223443.png
).
When the reference is relative, by default the referenced item is looked in the path
relative to the current file location in the destination directory (e.g. with the
preceding example, if the file is build/bar/index.html
, then transformed index.html
will be in dist/bar
, and usemin
will look for dist/bar/../images/foo.32323.png
).
Use cases
Simple one
|
+- app
| +- index.html
| +- assets
| +- js
| +- foo.js
| +- bar.js
+- dist
We want to optimize foo.js
and bar.js
into optimized.js
, referenced using relative path. index.html
should contain the following block:
<!-- build:js assets/js/optimized.js -->
<script src="assets/js/foo.js"></script>
<script src="assets/js/bar.js"></script>
<!-- endbuild -->
We want our files to be generated in the dist
directory.
By using the following useminPrepare
config:
{
useminPrepare: {
html: 'app/index.html',
options: {
dest: 'dist'
}
}
}
This will, on the fly, generate the following configuration:
{
concat:
{
'.tmp/concat/assets/js/scripts.js': [
'app/assets/js/app.js',
'app/assets/js/services.js'
]
},
uglify:
{
'dist/assets/js/scripts.js': [ '.tmp/concat/assets/js/scripts.js' ]
}
}
HTML file and asset files in sibling directories
app
|
+- html
| +- index.html
+- assets
| +- js
| +- foo.js
| +- bar.js
+- dist
We want to optimize foo.js
and bar.js
into optimized.js
, referenced using absolute path. index.html
should contain the following block:
<!-- build:js /assets/js/optimized.js -->
<script src="/assets/js/foo.js"></script>
<script src="/assets/js/bar.js"></script>
<!-- endbuild -->
We want our files to be generated in the dist
directory.
By using the following useminPrepare
config:
{
useminPrepare: {
html: 'html/index.html',
options: {
root: 'app'
dest: 'dist'
}
}
}
This will, on the fly, generate the following configuration:
{
concat:
{
'.tmp/concat/assets/js/scripts.js': [
'app/assets/js/app.js',
'app/assets/js/services.js'
]
},
uglify:
{
'dist/assets/js/scripts.js': [ '.tmp/concat/assets/js/scripts.js' ]
}
}
License
BSD license and copyright Google