只要gulp-watch检测到文件更改，就打印新消息

Question

I am using google-closure-compiler and gulp-watch to compile js files whenever any one of them is changed.

This is the code;

var closureCompiler = require('google-closure-compiler').gulp();
var flatmap = require('gulp-flatmap');    
var watch = require('gulp-watch');

gulp.task('js-closure', function () {
    return watch(['app/js/*.js', 'dist/single.js'], function()
    {
        gulp.src(['app/js/*.js', 'dist/single.js'], {base: './'})
            .pipe(flatmap(function(stream, file) {
                return stream.pipe(closureCompiler({
                    compilation_level: 'SIMPLE_OPTIMIZATIONS',
                    warning_level: 'QUIET',
                    language_in: 'ECMASCRIPT6_STRICT',
                    language_out: 'ECMASCRIPT5_STRICT',
                    output_wrapper: '(function(){\n%output%\n}).call(this)',
                    js_output_file: path.basename(file.path).replace(/js$/, 'min.js')
                }))
            }))
            .pipe(gulp.dest('./dist/js'));
    });
});

It works fine. However, I would like to print new messages to the terminal when js files detected to have changed and re-compiled. The new messages should provide information like this;

1201hrs - file XXX was changed and recompiled

Any form of logging would be welcomed.

Answer 1

Use gulp-changed-in-place , it only passes through source files that have changed. gulp-logger is a basic stream logger.

var gulp = require("gulp"),
    changedInPlace = require("gulp-changed-in-place"),
    logger = require("gulp-logger");

gulp.task("default", function () {
  return gulp.src("app/js/**/*.js")
    .pipe(changedInPlace())
    // the pipe now contains the files
    // that have changed since the last run
    .pipe(logger({
      before: "Closure compiler task",
      after: "Compiling complete!",
      showChange: true
    }))
    // your own gulp task goes here


    // then pipe to the destination
    .pipe(gulp.dest("./dist/js"));
});

Answer 2

Here is the modification required on your source code provided in the question. Credit goes to Dan Nagle who provided the tip on using gulp-changed-in-place and gulp-logger .

var closureCompiler = require('google-closure-compiler').gulp();
var flatmap = require('gulp-flatmap');
var watch = require('gulp-watch');
var changedInPlace = require("gulp-changed-in-place");
var logger = require("gulp-logger");

gulp.task('js-closure', function () {
    return watch(['app/js/*.js', 'dist/single.js'], function()
    {
        gulp.src(['app/js/*.js', 'dist/single.js'], {base: './'})
            .pipe(changedInPlace())
            .pipe(flatmap(function(stream, file) {
                return stream.pipe(closureCompiler({
                    compilation_level: 'SIMPLE_OPTIMIZATIONS',
                    warning_level: 'QUIET',
                    language_in: 'ECMASCRIPT6_STRICT',
                    language_out: 'ECMASCRIPT5_STRICT',
                    output_wrapper: '(function(){\n%output%\n}).call(this)',
                    js_output_file: path.basename(file.path).replace(/js$/, 'min.js')
                }))
            }))
            .pipe(logger({
                before: "file was changed",
                after: "file has been recompiled",
                showChange: true
            }))
            .pipe(gulp.dest('./dist/js'));
    });
});