Grunt plugins define tasks that implement certain build steps and can be reused across multiple projects. The examples will use the plugin "grunt-contrib-uglify". Check the Grunt website for a list of available plugins.
The first step to using an existing Grunt plugin is to install it.Grunt plugins are packaged as node modules and can be installed using npm like this:
npm install --save-dev grunt-contrib-uglify
This will install the Grunt plugin "grunt-contrib-uglify" locally into the node_modules folder (cf. npm folders).
Plugins must be installed locally to avoid version conflicts when working with multiple projects.
Specifying --save-dev as option automatically adds this Grunt plugin to the "devDependency" section in the package.json file. This file lists all node dependencies of a project.
Adding the Grunt plugin there will allow other developers working on the project to simply run npm install to locally install these required dependencies.
Now that the plugin is installed, it is time to tell Grunt about it and let it load all defined tasks. To do this, add the following line to your Gruntfile.js:
grunt.loadNpmTasks('grunt-contrib-uglify')
This line should be added within the top level function scope (not the initConfig section) where other grunt.registerTask() calls are made.
Since v1.2.0, Grunt will load its plugins that are located in any location that is visible to Node.js and NPM, instead of node_modules directly inside package that have a dev dependency to these plugins.
Plugin tasks can be run like other Grunt tasks either by specifying them on the command line:
grunt uglify
Or by registering a new task alias which calls this task, and running that task:
grunt.registerTask("dist", ["uglify"])
Plugin configuration depends on the specific plugin, so check the plugin's documentation for further information. Generally the configuration is located in the initConfig section of the Gruntfile.
TODO: Configuration Targets/options (Merge [Configuring tasks](Configuring tasks)?)