preProc loader module for webpack.

• Grunt plugin: grunt-pre-proc
• gulp plugin: gulp-pre-proc

The super simple preprocessor for front-end development.
See preProc for options and more information about preProc.

npm install --save-dev pre-proc-loader pre-proc

Documentation:

• Loaders
• Using loaders (for webpack v1)

For example:

// app.js

// The line below is removed.
TEST_MODE = true; // [DEBUG/]

// The HTML code for "button A" is picked from buttons.html file, and it inserted to "panel".
var buttonA = require('./buttons.html?tag=BUTTON-A'); // `tag` argument for pickTag method.
document.getElementById('panel').innerHTML = buttonA;

// webpack.config.js
module.exports = {
  entry: './app.js',
  output: {
    filename: 'bundle.js'
  },
  module: {
    rules: [
      {
        test: /\/develop\//,
        loader: 'pre-proc-loader',
        // Remove `DEBUG` contents from all files in `dir1` directory and all JS files.
        options: {removeTag: {tag: 'DEBUG', pathTest: ['/path/to/dir1', /\.js$/]}}
      },
      {
        test: /\.html$/,
        loader: 'pre-proc-loader',
        options: {pickTag: {}} // `tag` is specified via query string
      }
    ]
  }
};

You can specify options via query parameters or an options (or preProcLoader for webpack v1) object in webpack configuration.

If removeTag option is specified, call removeTag method with current content.

You can specify an object that has properties as arguments of the method.
Following properties are accepted:

• tag
• pathTest

Also, you can specify common values for the arguments into upper layer. That is, the options.pathTest is used when options.removeTag.pathTest is not specified.
And also, you can specify values for tag argument via a query string with the resource file like ?tag=TAG, and it is the first-priority value. An array also can be specified, like ?tag[]=TAG1,tag[]=TAG2, ?{tag:[TAG1,TAG2]} or ?tag=TAG1%2CTAG2 (or ?tag=TAG1%20TAG2, i.e. the values separated by space or comma).

If the pathTest is specified, current source file path is tested with the pathTest.

For example:

// webpack.config.js
// ...
// pre-proc-loader options
{
  tag: 'DEBUG',           // common
  pathTest: '/path/to',   // common

  removeTag: {},                            // tag: 'DEBUG', pathTest: '/path/to'
  replaceTag: {tag: ['SPEC1', 'SPEC2']},    // tag: ['SPEC1', 'SPEC2'], pathTest: '/path/to'
  pickTag: {}                               // tag: 'DEBUG', pathTest: '/path/to'
}
// For `file.html?tag=SPEC3` resource, the `SPEC3` is used for all method.

If replaceTag option is specified, call replaceTag method with current content.

You can specify arguments by the same way as the removeTag.
Following arguments are accepted:

• tag
• pathTest
• replacement (As options.replaceTag.replacement, not options.replacement)

If pickTag option is specified, call pickTag method with current content.

You can specify arguments by the same way as the removeTag.
Following arguments are accepted:

• tag
• allowErrors (As options.pickTag.allowErrors, not options.allowErrors)

When the tag was not found, this method throws an error by default. If true is specified for allowErrors, it returns null (not a string) without error. It is useful for handling unknown source code.
Also, you can specify options to call multiple methods, and other methods are not called when the tag was not found.

Type: boolean
Default: false

When the content is not JavaScript code (e.g. HTML, CSS, JSON, etc.), a loader that is specified as a final loader has to convert the content to JavaScript code and output it to allow another code to import the content.
If true is specified for toCode option, the content is converted to JavaScript code.
If the loader is specified as not a final loader, this option is ignored (i.e. the content is not converted, and it is passed to next loader).