preschool

Given a request for a preprocessor/transpiler/templating engine/postprocessor, spits back a function of the form function(err, compiled).

The specifications are highly extensible. Initial specs support wide range of functions (from Typescript to ES2015 to minification and cleaning). Pull requests and tests welcome! See instructions on writing a specification below.

Installation

$ npm install preschool

Examples

var compileHandlebars = preschool("handlebars");
 
compileHandlebars("<div>Hello, {{ name }}!</div>", { name : "Mickey" }, function(err, compiled) {
  console.log(compiled);
  // <div>Hello, Mickey!</div>
});
 
// Don't "npm install" missing modules (defaults to installing)
var compileHandlebars = preschool("handlebars", { fetch : false });
// => Throws error if handlebars is missing
 
// "npm install" to different directory
var compileHandlebars = preschool("handlebars", { dir : process.cwd() });

API

preschool ⇒ function
.defaultEngineForExtension(ext) ⇒ String

preschool ⇒ function

Loads a processor (templating, transpiler, minification), and standardizes callback to be fn(err, compiled). Defaults to npm install packages if they are missing. To disable, set options.fetch to false;

Most packages are referenced by their npm name, common exceptions include: javascript, html, css, es2015, and react.

Note that the callback is node style (err, compiled).

Returns: function - Processor of format fn(str, options, next)

Param	Type	Description
name	String	Name of module (npm install name).
options	Object	Options include {fetch} and {dir} (install directory).

Example

preschool("typescript")
  // => fn(str, options, next) for typescript

preschool.defaultEngineForExtension(ext) ⇒ String

Returns the default engine for an extension. Leading "." is removed.

Returns: String - Name of the default engine.

Param	Type	Description
ext	String	The file extension.

Example

preschool.defaultEngineForExtension("ts");
  // => "typescript"

Specifications

Specifications make use of JavaScript's eval. While using eval is typically considered to be bad form, when calling another function the performance does not appear suffer in V8. See http://jsperf.com/eval-function-call.

A specification consists of the following:

Param	Type	Description
name	String	Name of engine (by convention we use npm package name)
ext	String	Typical file extension (e.g. handlebars uses hbs)
type	String	Type of output file (html, css, js)
modules	Array	Array of required modules
syntax	String	The function to be evaluated

Example specification

{
  "name"    : "handlebars",
  "ext"     : "hbs",
  "type"    : "html",
  "modules" : ["consolidate", "handlebars"],
  "syntax"  : "handlebars.render(str, options, next)"
}

Looking up a specification by extension

Specifications is processed as an array. The first specification with ext is assumed to be the default for extension ext. This is why css, html and js are located at the top of the specification.

Writing a specification

The syntax processor does the following:

1. Prepends $0 to the string if string doesn't contain $0.
2. Replaces all $x with modules[x]. This allows incorporate of modules array.
3. Creates function that evaluates command. Note that str, options and next have special meanings.

Using Handlebars as an example:

// Input
handlebars.render(str, options, next)
 
// Interim
modules[0].handlebars.render(str, options, next)
 
// Equivalent function
function(str, options, next) { consolidate.handlebars.render(str, options, next); }

License

MIT