gulp-filter

概念

gulp.filter可以虛擬文件流中過濾特定的文件，可以當做是gulp.src的二次過濾，並且還可以restore操作恢復過濾前的gulp.src一次過濾的虛擬文件流。

安裝

$ npm install –save-dev gulp-filter

使用

1.只過濾文件
You may want to just filter the stream content:

const gulp = require('gulp');
const uglify = require('gulp-uglify');
const filter = require('gulp-filter');

gulp.task('default', () => {
    // Create filter instance inside task function
    const f = filter(['**', '!*src/vendor']);

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

2.過濾文件，並恢復文件流

const gulp = require('gulp');
const uglify = require('gulp-uglify');
const filter = require('gulp-filter');

gulp.task('default', () => {
    // Create filter instance inside task function
    const f = filter(['**', '!*src/vendor'], {restore: true});

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

3.多個過濾
By combining and restoring different filters you can process different sets of files with a single pipeline.

const gulp = require('gulp');
const less = require('gulp-less');
const concat = require('gulp-concat');
const filter = require('gulp-filter');

gulp.task('default', () => {
    const jsFilter = filter('**/*.js', {restore: true});
    const lessFilter = filter('**/*.less', {restore: true});

    return gulp.src('assets/**')
        .pipe(jsFilter)
        .pipe(concat('bundle.js'))
        .pipe(jsFilter.restore)
        .pipe(lessFilter)
        .pipe(less())
        .pipe(lessFilter.restore)
        .pipe(gulp.dest('out/'));
});

4.恢復成一個文件
You can restore filtered files in a different place and use it as a standalone source of files (ReadableStream). Setting the passthrough option to false allows you to do so.

const gulp = require('gulp');
const uglify = require('gulp-uglify');
const filter = require('gulp-filter');

gulp.task('default', () => {
    const f = filter(['**', '!*src/vendor'], {restore: true, passthrough: false});

    const stream = gulp.src('src/**/*.js')
        // Filter a subset of the files
        .pipe(f)
        // Run them through a plugin
        .pipe(uglify())
        .pipe(gulp.dest('dist'));

    // Use filtered files as a gulp file source
    f.restore.pipe(gulp.dest('vendor-dist'));

    return stream;
});

參數：

filter(pattern, [options])
Returns a transform stream with a .restore property.

1.pattern
Type: string Array Function

Accepts a string/array with globbing patterns which are run through multimatch.
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:
filter(file => /unicorns/.test(file.path));

2.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.