transform-chain

Build a chain of transforms

Provides a means of managing a list of transforms. Built with require.extensions transforms in mind, but not limited to that use case.

Install

$ npm install --save transform-chain

Usage

import TransformChain from 'transform-chain';
const chain = new TransformChain();

chain.appendTransform((code, filename, next) => {
  // true if downstream transforms want to manipulate this file too.
  next.hasMatch(filename); 

  // transform the code - no additional transforms applied
  return doTransform(code);
  
  // transform the code and forward it down the chain
  return next(doTransform(code), filename);
  
  // forward down the chain, and perform the transform after
  return doTransform(next(code, filename));
});

This module is also my first attempt at auto generating documentation using documentation.js and JSDoc.

HTML Documentation: http://jamestalmage.github.io/transform-chain/

API

TransformChain

Creates a new transform chain.

appendTransform

Appends a transform to the end of the chain.

Parameters

• transform Transform or TransformDefinition the transform to append.

hasMatch

Check if the chain has a matching transform for a particular file.

Parameters

• filename string the path to the file.

Returns boolean true if at least one transform in the chain matches the file.

notifyPostLoadHooks

Notify every transform that a file has been loaded. Included for legacy istanbul support.

Parameters

• filename string Passed to every transforms postLoadHook (regardless of whether the transform matches the loaded file).

prependTransform

Prepends a transform at the beginning of the chain.

Parameters

• transform Transform or TransformDefinition the transform to prepend.

transform

Transform an input using the matching transforms from the chain.

Parameters

• code Any The object to be transformed using the chain. Usually this will always be a string, but it is not required. Whatever type it is. All transforms in the chain must support it.
• filename string

Returns Any The transformed results. Again, this is almost always going to be a string.

Transform

Create a new transform.

Parameters

• opts Object or transformCallback
  • opts.transform [transformCallback] The transform function. (optional, default noop)
  • opts.match [Function or string or Array<string> or RegExp] Used to filter whether or not this transform is applied to a given file.
  • opts.extensions [Array<string>] List of file extensions this transform applies to. (optional, default '.js')
  • opts.verbose [boolean] If true, every invocation of the transform will be logged. (optional, default false)
  • opts.name [string] The name of this transform, used in logging and error reporting.

Returns Transform A new transform instance

matches

Check whether this transform should be applied to a given file. transformCallback

Parameters

• filename string The name of the file

Returns boolean true if this transform should be applied to the file.

transform

Perform the transform. Called with the same parameters as transformCallback.

Parameters

• code string or Any
• filename string
• next Function

Returns string or Any

transformCallback

A callback that performs a transform

Parameters

• code string or Any The input to be transformed.
• filename string The name of the file being transformed.
• next Function Execute the rest of the transform synchronously
  • next.hasNext Function Check if any of the transforms remaining in the chain can handle the file. You can optionally pass a string to change the name of the file.

License

MIT © James Talmage