Build configuration files are JSON files that are used to determine what should be exported from the library and what options should be passed to the compiler.

exports - Array.<string> An array of symbol names or patterns to be exported (names that are used in your application). For example, including "ol.Map" will export the map constructor. Method names are prefixed with #. So "ol.Map#getView" will export the map's getView method. You can use a * at the end to match multiple names. The pattern "ol.Map#*" will export all map methods.
compile - Object An object whose properties are Closure Compiler options. Property names match the option names without the -- prefix (e.g. "compilation_level": "ADVANCED_OPTIMIZATIONS" would set the --compilation_level option). Where an option can be specified multiple times, use an array for the value (e.g. "externs": ["one.js", "two.js"]). Where an option is used as a flag, use a boolean value (e.g. "use_types_for_optimization": true).

Below is a complete build.json configuration file that would generate a build including every symbol in the library (much more than you'd ever need).

{
  "exports": ["*"],
  "compile": {
    "compilation_level": "ADVANCED_OPTIMIZATIONS",
    "use_types_for_optimization": true,
    "externs": [
      "externs/olx.js",
      "externs/oli.js",
      "externs/geojson.js"
    ],
    "define": [
      "ol.ENABLE_PROJ4JS=false",
      "goog.dom.ASSUME_STANDARDS_MODE=true",
      "goog.DEBUG=false"
    ],
    "output_wrapper": "(function(){%output%})();"
  }
}

To generate a build named ol.min.js with the build.json, you would run this:

node tasks/build.js build.json ol.min.js

`generate-exports.js`

Called internally to generate a build/exports.js file optionally with a limited set of exports.

`generate-symbols.js`

Called internally to parse the library for API annotations and write out a build/symbols.json file.

`parse-examples.js`

Called after install to generate an example index. After new examples are added, run node tasks/parse-examples.js to regenerate the example index.

`serve.js`

Run a debug server that provides all library sources unminified. Provides a static server for examples and tests. See the --help option for more detail.

node tasks/serve.js --help