gulp-firstline-filter

Filter files by first line in a gulp stream
Enables you to work on a subset of the original files by filtering them using glob patterns. When you're done and want all the original files back you just use the restore stream.

Install

``
$ npm install --save-dev gulp-firstline-filter
`




Usage

$3

You may want to just filter the stream content:

`js
const gulp = require('gulp');
const babel = require('gulp-babel');
const filter = require('gulp-firstline-filter');

gulp.task('default', () => {
// Create filter instance inside task function
const f = filter(/es6/);

return gulp.src('src/*/.js')
// Filter a subset of the files
.pipe(f)
// Run them through a plugin
.pipe(babel())
.pipe(gulp.dest('dist'));
});
`

$3

`js
const gulp = require('gulp');
const babel = require('gulp-babel');
const filter = require('gulp-firstline-filter');

gulp.task('default', () => {
// Create filter instance inside task function
const f = filter(/es6/, {restore: true});

return gulp.src('src/*/.js')
// Filter a subset of the files
.pipe(f)
// Run them through a plugin
.pipe(babel())
// Bring back the previously filtered out files (optional)
.pipe(f.restore)
.pipe(gulp.dest('dist'));
});
`

$3

`js
const gulp = require('gulp');
const babel = require('gulp-babel');
const filter = require('gulp-firstline-filter');

gulp.task('default', () => {
// Create filter instance inside task function
const f = filter((firstline) => !(/es6/.test(firstline)), {restore: true});

return gulp.src('src/*/.js')
// Filter a subset of the files
.pipe(f)
// Run them through a plugin
.pipe(babel())
// Bring back the previously filtered out files (optional)
.pipe(f.restore)
.pipe(gulp.dest('dist'));
});
`

API

$3

Returns a transform stream with a .restore property.

#### pattern

Type: RegExp Function

Accepts a RegExp or function

If you supply a function, you'll get a vinyl file object as the first argument and you're expected to return a boolean of whether to include the file:

`js
filter(firstline => /unicorns/.test(firstline));
`

#### options

Type: Object

Accepts minimatch options.

Note: Set dot: true if you need to match files prefixed with a dot (e.g. .gitignore).

##### restore

Type: boolean

Default: false

Restore filtered files.

##### passthrough

Type: boolean

Default: true

When set to true, filtered files are restored with a PassThrough stream, otherwise, when set to false, filtered files are restored as a ReadableStream.

When the stream is a ReadableStream, it ends by itself, but when it's PassThrough`, you are responsible of ending the stream.