preprocess
Advanced tools
Preprocess directives in HTML, JavaScript, etc directives based off variable context
Preprocess HTML, JavaScript, and other files with directives based off custom or ENV configuration
Install via npm:
$ npm install --save preprocess
<head>
<title>Your App</title>
<!-- @if NODE_ENV='production' -->
<script src="some/production/lib/like/analytics.js"></script>
<!-- @endif -->
</head>
<body>
<!-- @ifdef DEBUG -->
<h1>Debugging mode - <!-- @echo RELEASE_TAG --> </h1>
<!-- @endif -->
<p>
<!-- @include welcome_message.txt -->
</p>
</body>
var configValue = '/* @echo FOO */' || 'default value';
// @ifdef DEBUG
someDebuggingCall()
// @endif
The most basic usage is for files that only have two states, non-processed and processed.
In this case, your @exclude directives are removed after preprocessing
<body>
<!-- @exclude -->
<header>You're on dev!</header>
<!-- @endexclude -->
</body>
After build
<body>
</body>
@if VAR='value' / @endif
This will include the enclosed block if your test passes@ifdef VAR / @endif
This will include the enclosed block if VAR is defined (typeof !== 'undefined')@ifndef VAR / @endif
This will include the enclosed block if VAR is not defined (typeof === 'undefined')@include
This will include the source from an external file. If the included source ends with a newline then the
following line will be space indented to the level the @include was found.@include-static
Works the same way as @include but doesn't process the included file recursively. Is useful if a large
file has to be included and the recursive processing is not necessary or would otherwise take too long.@extend file.html / @endextend
This will use the source from the external file indicated with the @extend tag to wrap the enclosed block.@extendable
This tag is used to indicate the location in a file referenced using @extend where the block enclosed by @extend will be populated.@exclude / @endexclude
This will remove the enclosed block upon processing@echo VAR
This will include the environment variable VAR into your source@foreach $VAR in ARR / @endfor
This will repeat the enclosed block for each value in the Array or Object in ARR. Each value in ARR can be interpolated into the resulting content with $VAR.@exec FUNCTION([param1, param2...])
This will execute the environment FUNCTION with its parameters and echo the result into your source. The parameter
could be a string or a reference to another environment variable.This is useful for more fine grained control of your files over multiple environment configurations. You have access to simple tests of any variable within the context (or ENV, if not supplied)
<body>
<!-- @if NODE_ENV!='production' -->
<header>You're on dev!</header>
<!-- @endif -->
<!-- @if NODE_ENV='production' -->
<script src="some/production/javascript.js"></script>
<!-- @endif -->
<script>
var fingerprint = '<!-- @echo COMMIT_HASH -->' || 'DEFAULT';
</script>
<script src="<!-- @exec static_path('another/production/javascript.js') -->"></script>
</body>
With a NODE_ENV set to production and 0xDEADBEEF in
COMMIT_HASH this will be built to look like
<body>
<script src="some/production/javascript.js"></script>
<script>
var fingerprint = '0xDEADBEEF' || 'DEFAULT';
</script>
<script src="http://cdn2.my.domain.com/another/javascript.js"></script>
</body>
With NODE_ENV not set or set to dev and nothing in COMMIT_HASH, the built file will be
<body>
<header>You're on dev!</header>
<script>
var fingerprint = '' || 'DEFAULT';
</script>
<script src="http://localhost/myapp/statics/another/javascript.js"></script>
</body>
You can also have conditional blocks that are hidden by default by using the
fictional !> end tag instead of --> after your condition:
<!-- @if true !>
<p>Process was run!</p>
<!-- @endif -->
Extended syntax below, but will work without specifying a test
normalFunction();
//@exclude
superExpensiveDebugFunction()
//@endexclude
anotherFunction('/* @echo USERNAME */');
Built with a NODE_ENV of production :
normalFunction();
anotherFunction('jsoverson');
Like HTML, you can have conditional blocks that are hidden by default by ending the directive with a ** instead of */
angular.module('myModule', ['dep1'
, 'dep2'
/* @if NODE_ENV='production' **
, 'prod_dep'
/* @endif */
/* @exclude **
, 'debug_dep'
/* @endexclude */
]);
Note: Hidden by default blocks only work with block comments (/* */) but not with line comments (//).
CSS example
body {
/* @if NODE_ENV=='development' */
background-color: red;
/* @endif */
}
// @include util.css
(CSS preprocessing supports single line comment style directives)
#!/bin/bash
# @include util.sh
Preprocesses a source provided as a string and returns the preprocessed source.
Type: String (mandatory)
The source to preprocess.
Type: Object
Default: process.env
The context that contains the variables that are used in the source. For @extend variants and @include the additional
context property src is available inside of files to be included that contains the current file name. This property is also
available in the context of the source file if one of the preprocessFile*() API variants are used.
Type: Object
The options object allows to pass additional options to preprocess. Available options are:
Type: Boolean
Default: false
When using @include variants and @extend, preprocess will by default throw an exception in case an included
file can't be found. Set this option to true to instruct preprocess to fail silently and instead of throwing
to write a message inside of the preprocessed file that an included file could not be found.
Type: String
Default: process.cwd()
The directory where to look for files included via @include variants and @extend.
Type: String
Default: EOL of source string or os.EOL if source string contains multiple different or no EOLs.
The end of line (EOL) character to use for the preprocessed result. May be one of:
\r\n - Windows\n - Linux/OSX/Unix\r - legacy MacType: String
Default: html
The syntax type of source string to preprocess. There are 3 main syntax variants:
html, aliases: xmljs, aliases: javascript, jsx, json, c, cc, cpp, cs, csharp, java, less, sass, scss, css, php,
ts, tsx, peg, pegjs, jade, stylcoffee, aliases: bash, shell, shPreprocesses a sourceFile and saves the result to destFile. Simple wrapper around fs.readFile() and fs.writeFile().
Type: String (mandatory)
The path to the source file to preprocess.
Type: String (mandatory)
The path to the destination file where the preprocessed result shall be saved.
See context attribute description of preprocess() function.
Type: function(err)
The callback function that is called upon error or completion. Receives an error if something goes wrong as first parameter.
See options attribute description of preprocess() function. Differs only in that the default srcDir value is set
to the path of the provided source file instead of process.cwd() and the default type is derived from source file extension.
Preprocesses a sourceFile and saves the result to destFile. Simple wrapper around fs.readFileSync() and fs.writeFileSync().
Type: String (mandatory)
The path to the source file to preprocess.
Type: String (mandatory)
The path to the destination file where the preprocessed result shall be saved.
See context attribute description of preprocess() function.
See options attribute description of preprocess() function. Differs only in that the default srcDir value is set
to the path of the provided source file instead of process.cwd() and the default type is derived from source file extension.
var pp = require('preprocess');
var text = 'Hi, I am <!-- @echo USERNAME -->';
pp.preprocess(text);
// -> Hi, I am jsoverson
pp.preprocess(text, {USERNAME : "Bob"});
// -> Hi, I am Bob
// specify the format to use for the directives as the third parameter
pp.preprocess(text, {USERNAME : "Bob"}, {type: 'html'});
// -> Hi, I am Bob
// Preprocess files asynchronously
pp.preprocessFile(src, dest, context, callback, options);
// Preprocess files synchronously
pp.preprocessFileSync(src, dest, context, options);
In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using jshint
3.1.0
.jsx file extension as an alias for js (@BendingBender, #79).tsx file extension as an alias for js (@rosendi, #100)3.0.1/2 Fixes for backward compatibility and regex cleanups (thanks to @anseki for suggestions, #77)
3.0.0
Breaking changes:
@include or @extend can not be found, preprocess will now throw by default
with a possibility to opt in to the legacy behavior via the fileNotFoundSilentFail option (@BendingBender, #35).srcDir option was moved to the options object and now defaults to process.cwd instead of throwing by
default (@BendingBender, #68)New functionality:
@if/@endif) are now processed recursively (@Frizi, #61)js (@mallowigi, #40) and html (@Frizi, #66)Fixes:
@exec in files included via @include and @extend (@BendingBender, #58)@extend and @exclude html regex so that directives may appear more than once in one line (@BendingBender, #36)@if and @foreach to not require trailing whitespace (@BendingBender, #74)2.3.1 Fixed @echo and @exec directives to allow - and * characters, fixed @exec with multiple params (@BendingBender, #21, #45, #51, #54).
2.3.0 Added support for @include-static (@BendingBender)
2.2.0 Added support for @foreach and @extend (@orionstein)
2.1.1 Added support for .styl files via js regex (@nsonnad)
2.1.0 Added automatic support for numerous formats, merged @exec, hidden by default html tags, added simple directives
2.0.0 Added ability to echo strings, added conditional comments, removed lodash, merged 17, 13, 15, 16
1.2.0 Added processing for hash-style comments (@marsch). Added more file aliases.
1.1.0 Added deep inclusion, fixed sequential ifs
1.0.1 Fixed multiple inline echo statements
1.0.0 Pulled from grunt-preprocess to stand alone
Copyright Jarrod Overson
Written by Jarrod Overson
Licensed under the Apache 2.0 license.
FAQs
Preprocess directives in HTML, JavaScript, etc directives based off variable context
The npm package preprocess receives a total of 12,765 weekly downloads. As such, preprocess popularity was classified as popular.
We found that preprocess demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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