Check out the newly updated wiki!
See the wiki for information about using curl.js with jQuery, dojo, or underscore.
- 0.7.5
- Can now resolve relative plugin ids in local require (bug fix).
- 0.7.4
- curl.js is now available on CDN: http://cdnjs.com/#curl and http://jsdelivr.com/#!curl.js
- "main" modules specified in config are fetched after a delay for better compatibility with bundles.
- cram.js support
- data-curl-run attribute for loading run.js files.
- fix to stop IE6-8 complaining about sourceURL when @cc_on.
- new debug dist version of curl.js.
- bug fixes for running curl.js inside node.js.
- 0.7.3
- css! plugin no longer fails when sniffing for Opera (Fixes #147)
- new curl.config() API method
- curl(config) and curl.config() can be called repeatedly (fixes #146)
- new "main" {String|Array} config option to init loading of main modules for an application
- new i18n plugin (fixes #26)
- 0.7.2
- css! plugin now works everywhere (closed an Opera-XDomain issue).
- css! plugin now returns the stylesheet created (as it used to, but for all browsers).
- curl() error handler is called even if no success handler is specified.
- 0.7.1
- fixed inability to load non-anonymous "main" modules (packages) (also #138)
- restored ability to use urls in place of module ids as dependencies
- fixed duplicate downloads/execution of modules if dev specified module in two different ways (e.g. as module and as url) (#137)
- fixed early callback in IE under load (#136)
- restored plugin-specific config and paths
- 0.7.0
- new module.config() method when using CommonJS-wrapped modules
- dontAddFileExt config option (RegExp or string) decides whether or not to add a .js file extension to module urls.
- Implement error callbacks in require() and plugin load() methods.
- Improved css! plugin no longer fails on blank stylesheets and supports all features in all browsers (except for error callbacks in Opera, IE6, Safari 5 (and below) and Firefox 8 (and below)).
- shell scripts now work in more environments
- many other fixes
TODO:
- document plugin configuration options and how to use each plugin
- notes about using JSONP (it works for objects, arrays, functions, numbers and strings! use ?callback=define)
curl.js is a small and very fast AMD-compliant asynchronous loader. Size: <4KB (gzipped) using Google's Closure Compiler.
If you'd like to use curl.js for non-AMD modules (ordinary javascript files), you'll want to use a version with the js! plugin built in. You may also want to build-in the domReady module.
curl.js, like all async loaders, cannot circumvent browsers' security
restrictions when using the file: protocol. Therefore, you must use
curl from a page served from a web server (i.e. using http: or https:).
Trying to run curl.js from a page loaded from your local file system
will not work correctly.
What the heck is "cujo"? cujoJS is a web app development platform. See the bottom of this file for more info.
What is "cram"? cram (cujo resource assembler) is the build tool companion to curl.js. You use cram to compile all of your modules into a small number of javascript files which are loaded much faster into the browsers.
- Loads CommonJS AMD-formatted javascript modules in parallel (fast!)
- Loads CommonJS Modules (v1.1 when wrapped in a
define()) (fast!) - Loads CommonJS Packages (v1.1 modules wrapped in a
define()) (fast!) - Loads non-AMD javascript files in parallel, too (fast! via js! plugin)
- Loads CSS files and text files in parallel (fast! via plugins)
- Waits for dependencies (js, css, text, etc) before executing javascript
- Waits for domReady, if/when desired
- Allows for virtually limitless combinations of files and dependencies
- Tested with Chrome, FF3+, Safari 3.2+, IE6-8, Opera 9.5+
Oh, did we mention? It's fast! It's even faster than the leading non-AMD script loaders.
- Go to the issues section of the curl repo (https://github.com/cujojs/curl/issues) and search for an answer to your question or problem.
- If no answer exists, file a new ticket! Somebody will typically respond within a few hours.
It's that easy.
Got more in-depth questions? Browse the cujojs discussion group.
For a complete description, check out the wiki.
curl(['dep1', 'dep2', 'dep3' /* etc */], callback);Loads dependencies and the executes callback.
- ['dep1', 'dep2', 'dep3']: Module names or plugin-prefixed resource files
- callback: Function to receive modules or resources. This is where you'd typically start up your app.
curl(['dep1', 'dep2', 'dep3' /* etc */])
.then(callback, errorback);Promises-based API for executing callbacks.
- ['dep1', 'dep2', 'dep3']: Module names or plugin-prefixed resource files
- callback: Function to receive modules or resources
- errorback: Function to call if an exception occurred while loading
- For full CommonJS Promises/A compliance, use when.js
when(curl(['dep1'])).then(callback);
curl(config, ['dep1', 'dep2', 'dep3' /* etc */], callback);Specify configuration options, load dependencies, and execute callback.
- config: Object containing curl configuration options (paths, etc.)
- ['dep1', 'dep2', 'dep3']: Module names or plugin-prefixed resource files
- callback: Function to receive modules or resources
curl(['domReady!', 'dep2', 'dep3' /* etc */])
.then(
callback,
errorback
);
curl(['dep1', 'dep2', 'domReady!' /* etc */], function (dep1, dep2) {
// do something here
});Executes the callback when the dom is ready for manipulation AND all dependencies have loaded.
- callback: No parameters except the domReady object
- errorback: Function to call if an exception occurred while loading
curl(['domReady!', 'js!nonAMD.js!order', 'js!another.js!order']), function () {
/* do something cool here */
});Executes the function when the non-AMD javascript files are loaded and the dom is ready. The another.js file will wait for the nonAMD.js file before executing.
curl(['js!nonAMD.js'])
.next(['dep1', 'dep2', 'dep3'], function (dep1, dep2, dep3) {
// do something before the dom is ready
})
.next(['domReady!'])
.then(
function () {
// do something after the dom is ready
},
function (ex) {
// show an error to the user
}
);Executes callbacks in stages using .next(deps, callback).
curl = {
baseUrl: '/path/to/my/js',
pluginPath: 'for/some/reason/plugins/r/here',
paths: {
curl: 'curl/src/curl',
cssx: 'cssx/src/cssx',
my: '../../my-lib/'
},
apiName: 'someOtherName'
};If called before the <script> that loads curl.js, configures curl.js. All of
the configuration parameters are optional. curl.js tries to do something sensible
in their absence. :)
- baseUrl: the root folder to find all modules, default is the document's folder
- paths: a mapping of module paths to relative paths (from baseUrl)
- pluginPath: the place to find plugins when they are specified without a path (e.g. "css!myCssFile" vs. "cssx/css!myCssFile") and there is no paths mapping that applies.
- apiName: an alternate name to
curlandrequirefor curl.js's global variable - apiContext: an object, rather than
window, to place curl on when usingapiName
define(['dep1', 'dep2', 'dep3' /* etc */], definition);
define(['dep1', 'dep2', 'dep3' /* etc */], module);
define(['dep1', 'dep2', 'dep3' /* etc */], promise);
define(module);
define(name, ['dep1', 'dep2', 'dep3' /* etc */], definition);
define(name, ['dep1', 'dep2', 'dep3' /* etc */], module);
define(name, ['dep1', 'dep2', 'dep3' /* etc */], promise);
define(name, module);Defines a module per the CommonJS AMD proposed specification.
- ['dep1', 'dep2', 'dep3']: Module names or plugin-prefixed resource files. Dependencies may be named 'require', 'exports', or 'module' and will behave as defined in the CommonJS Modules 1.1 proposal.
- definition: Function called to define the module
- module: Any javascript object, function, constructor, or primitive
- name: String used to name a module (not necessary nor recommended)
<script>
// configure curl
curl = {
paths: {
cssx: 'cssx/src/cssx/',
stuff: 'my/stuff/'
}
};
</script>
<script src="../js/curl.js" type="text/javascript"></script>
<script type="text/javascript">
curl(
// fetch all of these resources ("dependencies")
[
'stuff/three', // an AMD module
'cssx/css!stuff/base', // a css file
'i18n!stuff/nls/strings', // a translation file
'text!stuff/template.html', // an html template
'domReady!'
]
)
// when they are loaded
.then(
// execute this callback, passing all dependencies as params
function (three, link, strings, template) {
var body = document.body;
if (body) {
body.appendChild(document.createTextNode('three == ' + three.toString() + ' '));
body.appendChild(document.createElement('br'));
body.appendChild(document.createTextNode(strings.hello));
body.appendChild(document.createElement('div')).innerHTML = template;
}
},
// execute this callback if there was a problem
function (ex) {
var msg = 'OH SNAP: ' + ex.message;
alert(msg);
}
);
</script>The file structure for this example would look as follows:
js/
curl/
plugin/
i18n.js
text.js
domReady.js
cssx/
src/
cssx/
css.js
my/
stuff/
nls/
strings.js
base.css
template.html
three.js
curl.js
Web apps, especially large ones, require many modules and resources. Most of these modules and resources need to be loaded at page load, but some may be loaded later, either in the background or "just in time". They also need to be loaded as quickly as possible.
The traditional way to load javascript modules is via a <SCRIPT> element in
an HTML page. Similarly, CSS files are loaded via a <LINK> element, and
text resources are either loaded in the page or via XHR calls.
The problem with <SCRIPT> and <LINK> elements is that a browser must execute
them sequentially since it has no idea if one may depend on another. It just
assumes the developer has placed them in the correct order and that there are
dependencies. (The term "synchronous loading" is used to describe this process
since the elements are executed in a single timeline.)
If there are no dependencies between two files, loading them sequentially is a waste of time. These files could be loaded and executed in parallel (i.e at the same time).
An asynchronous loader does just that: it loads javascript files (and other types of files) in parallel whenever possible.
curl.js has lots of company. Other async loaders include LABjs, Steal.js, yepnope.js, $script.js, the Backdraft loader (bdLoad), and RequireJS.
Asynchronous Module Definition is the CommonJS proposed standard for javascript modules that can be loaded by asynchronous loaders. It defines a simple API that developers can use to write their javascript modules so that they may be loaded by any AMD-compliant loader.
The AMD proposal follows the CommonJS Modules proposal as much as possible. Because of the way browsers load and evaluate scripts, AMD can't follow it completely without causing significant processing overhead. Instead, AMD allows us to place a lightweight wrapper around javascript modules to help work around the shortcomings.
Ultimately, both proposals (AMD and Modules 1.1) are in preparation for an official javascript modules specification and eventual implementation in browsers.
If you don't want to wait for official javascript modules, then don't. The future is now. AMD works now -- and it's awesome.
AMD's API focuses on one globally-available function: define() and some
CommonJS-inspired variables, require(), exports, and module.
require() specifies a list of dependent modules or resources that must be
loaded before running a set of code. This code resides in a callback function
that is executed asynchronously, i.e. it runs later, not in the current
"thread". Specifically, it executes when all of the dependencies are loaded
and ready.
The proposal does not mandate that require() be specified globally. In fact,
at a global level, the concerns of a loader are about application bootstrapping
and not about finding dependencies. To keep the confusion about these two
concepts to a minimum, curl.js uses curl() for the public API. You may rename
this API back to require() by supplying the apiName config param
(apiName: "require"), but this is not receommended.
It's more important that the define() method be consistent. This is the
method that tells the loader what modules have been loaded by a script.
define() also specifies a list of dependencies and a callback function that
defines and/or creates the resource when the dependencies are ready.
Optionally, define() also takes a name parameter, but this is mainly for build
tools and optimizers.
Inside the define(), the require() method acts like other AMD loaders.
AMD's API also helps code reuse by providing compatibility with CommonJS
(server) modules. AMD-compliant loaders support the same require() syntax and
argument signatures as server-side javascript (ssjs) modules.
Not all async loaders are AMD-compliant. Of the list above, only the following are AMD-compliant:
curl.js http://github.com/cujojs/curl
RequireJS http://requirejs.org/
backdraft loader http://bdframework.org/bdLoad
The beauty of AMD loaders is their ability to remove the drudgery of manually managing dependencies. Since all dependencies are listed within the modules, the loader will ensure that everything is loaded into the browser -- and in the right order.
curl.js is much smaller than other AMD loaders. Less than 1/2 the size of the others in the list above. It's able to achieve this via a Promises-based design. (Promises are another CommonJS proposed standard.)
curl.js communicates with it's plugins via Promises, rather than a simple callback function. This allows proactive error handling, rather than detecting problems via a timeout, which can be tricky to set correctly. curl does this in a backwards-compatible way so AMD-compliant plugins will still work in curl.
curl.js will also return a promise from curl() calls. This allows you to
write code like this:
curl(
[
'myApp/moduleA',
'myApp/moduleB'
],
).then(
function success (A, B) {
// load myApp here!
},
function failure (ex) {
alert('myApp didn't load. reason: ' + ex.message);
}
);(When using require as a dependency, it does not return a promise.
This is so that 100% CommonJS compliance is assured inside modules.)
Yes, but why would you? Once you start using AMD, you'll never go back! :)
You may use non-AMD javascript files by specifying the js! plugin prefix like this:
curl(
[
'js!plainOldJsFile1.js!order',
'js!anotherPlainOldJsFile.js!order'
]
).then(
function () {
/* do something with your plain, boring javascript files */
},
function () {
/* do something if any fail to load */
}
);The !order suffix instructs curl.js to wait for previous scripts to execute
before executing the current script. All scripts download in parallel, though,
unless you specify prefetch: false in the config. Be sure to have proper
cache headers set if you plan to use prefetch: true or scripts will get
downloaded twice in browsers that don't support async="false".
Yes, curl.js follows the CommonJS Loader Plugin specification, so you can use any compatible plugin. The following plugins are included:
js! -- loads non-AMD javascript files. more info on the wiki
text! -- loads text files
link! -- loads css files via a link element (simple, fast)
css! -- loads css files (lots of options)
domReady! -- resolves when the dom is ready for manipulation
async! -- resolves when a module signals it's ready
The following plugins are in progress:
i18n! -- loads text strings and other locale-specific constants
Complete plugin docs are on the wiki.
curl.js uses <script> element injection rather than XHR/eval. This allows
curl.js to load cross-domain scripts as well as local scripts.
To find scripts and other resources, curl.js uses module names. A module name looks just like a file path, but typically without the file extension. If a module requires a plugin in order to load correctly, it will have a prefix delimited by a "!" and will also often have a file extension when a plugin may load different types of files.
Some examples of module names:
- dojo/store/JsonRest
- my/lib/string/format
- js!my/lib/js/plain-old-js.js
- css!my/styles/reset.css
- http://some-cdn/uber/module
By default, curl.js will look in the same folder as the current document's location.
For instance, if your web page is located at http://my-domain/apps/myApp.html,
curl.js will look for the JsonRest module at http://my-domain/apps/dojo/store/JsonRest.js.
You can tell curl.js to find modules in other locations by specifying a baseUrl or
individual paths for each of your libraries. For example, if you specify a baseUrl of
/resources/ and the following paths:
paths: {
dojo: "third-party/dojo",
css: "third-party/cssmojo/css",
my: "my-cool-app-v1.3",
"my/lib/js": "old-js-libs"
}Then the modules listed above will be sought in the following locations:
- /resources/third-party/dojo/store/JsonRest.js
- /resources/my-cool-app-v1.3/lib/string/format.js
- /resources/old-js-libs/plain-old-js.js
- /resources/my-cool-app-v1.3/styles/reset.css
- http://some-cdn/uber/module.js
Note: you will need to create a path to curl.js's plugins and other modules if the curl folder isn't directly under the same folder as your web page. curl.js uses the same mechanism to find its own modules.
AMD supports the notion of plugins. Plugins are AMD modules that can be used to load javascript modules -- or other types of resources. curl comes with several plugins already, including a text plugin (for templates or other text resources), two different css plugins, a dom-ready plugin, and several others.
Plugins are designated by a prefix on the name of the module or resource to be loaded. They are delineated by a ! symbol. The following example shows the use of some plugins:
define(
[
'text!myTemplate.html',
'css!myCssFile'
],
function (templateString, cssLinkNode) {
// do something with the template and css here
}
);Since plugins are just AMD modules, they would typically be referenced using their fully-pathed names. curl provides a pluginPath configuration option that allows you to specify the folder where [most of] your plugins reside so you don't have to specify their full paths. This also helps with compatibility with other AMD loaders that assume that certain plugins are bundled and internally mapped.
If one or more of your plugins does not reside in the folder specified by the pluginPath config option, you can use its full path or you can specify a path for it in curl's paths config object.
// example of a fully-pathed plugin under the cssx folder
define(['/css!myCssFile'], function (cssxDef) {
// do some awesome css stuff here
});Plugins can also have configuration options. Global options can be specified on curl's configuration object. Options can also be supplied to plugins via suffixes. Suffixes are also delineated by the ! symbol. Here's an example of a plugin using options:
// don't try to repair IE6-8 opacity issues in my css file
define(['css!myCssFile!ignore:opacity'], function (cssxDef) {
// do some awesome css stuff here
});- Learn about AMD-formatted javascript modules if you don't already know how.
- Clone or download curl to your local machine or server.
- Figure out the baseUrl and paths configuration that makes sense for your project.
- Check out the "API at a glance" section above to figure out which loading methodology you want to use.
- Study the "Very Simple Example" and some of the test files.
- Try it on your own files.
I have dozens (or hundreds) of modules. Even with parallel loading, the performance sucks! What can I do about that?
True! No parallel loader can lessen the latency required to create an HTTP connection. If you have dozens or hundreds of files to download, it's going to take time to initiate each of the connections.
However, there are tools to that are designed to fix this problem! There are builders and compilers. dojo users are probably already familiar with dojo's build tool and optimizer. RequireJS comes with a build tool and Google's Closure compiler.
The build tool is used to concatenate several modules (and/or resources) into just a few files. It does this by following the dependency chain specified in the define() and require() calls. You can specify which top-level modules or resources are in each file and the build tool finds the rest.
After the build tool creates the concatenated files, the files can be passed into a compiler (also called a shrinker or compressor).
We're writing curl to be compatible with RequireJS's build tool, but there's also another cujo project in the pipeline: cram. Cram is the Cujo Resource Assembler.
cujo.js supports the CommonJS Packages 1.1 specification. Packages are defined in the packages configuration parameter:
cujo = {
baseUrl: 'path/to/js',
packages: {
'my-package': {
path: 'path/to/my-package',
main: 'main/main-module-file',
lib: 'location/of/other/modules'
}
}
};The path property describes where to find the package in relation to the baseUrl parameter. The main and lib properties describe where to find modules inside the package. The main property gives the relative path to the package's main module. The lib property reflects the path to all other modules in the package.
In the example above, the main module of the package can be obtained as follows
curl(['my-package'], callback);and will be fetched from the following path:
path/to/js/path/to/my-package/main/main-module-file.js
Some other file in the package would be obtained as follows:
curl(['my-package/other-module'], callback);and will be fetched from the following path:
path/to/js/path/to/my-package/location/of/other/modules/other-module.js
cujo.js is a web app development platform. It employs MVC, IOC, AMD and lots of other TLAs. :) curl.js is one of the many micro-libs we're pulling out of cujo.js. Our goal is to make the advanced concepts in cujo.js more palatable by breaking them down into easier-to-grok chunks. Other cujo.js libs include:
- canhaz: a project and code bootstrapping tool that will save you tons of typing.
- wire: A light, fast, flexible Javascript IOC container
- when.js: A small, fast Promises/A compliant promises implementation
- cram: a javascript compressor, concatenator, and optimizer meant to be used with curl.js
Many thanks to Bryan Forbes (@bryanforbes) for helping to clean up my code and for making cujo's domReady much more robust. More about Bryan: http://www.reigndropsfall.net/
Kudos also to James Burke (@jrburke) who instigated the CommonJS AMD proposal and paved the way to create AMD-style loaders. More about James: http://tagneto.blogspot.com/
Shout out to Kris Zyp (@kriszyp) for excellent ideas and feedback and to Kyle Simpson (@getify) who is inarguably the godfather of javascript loading.