我正在尝试调用“gulp watch”命令，但它不起作用，它说:

module.js:340 
    throw err; 
    ^ 
 
Error: Cannot find module 'gulp-livereload' 
    at Function.Module._resolveFilename (module.js:338:15) 
    at Function.Module._load (module.js:289:25) 
    at Module.require (module.js:366:17) 
    at require (module.js:385:17) 
    at Object.<anonymous>    (/Applications/XAMPP/xamppfiles/htdocs/last/gulpfile.js:2:18) 
    at Module._compile (module.js:425:26) 
    at Object.Module._extensions..js (module.js:432:10) 
    at Module.load (module.js:356:32) 
    at Function.Module._load (module.js:313:12) 
    at Module.require (module.js:366:17) 
    at require (module.js:385:17) 

我猜这是因为我的 gulpfile.js 中的错误，但我不知道是什么原因。有人知道“livereload”发生了什么事吗？我在互联网上寻找答案，但找不到任何东西，我尝试(再次)安装 npm，但它不起作用。

var gulp = require('gulp'); 
var livereload = require('gulp-livereload') 
var uglify = require('gulp-uglifyjs'); 
var sass = require('gulp-sass'); 
var autoprefixer = require('gulp-autoprefixer'); 
var sourcemaps = require('gulp-sourcemaps'); 
var imagemin = require('gulp-imagemin'); 
var pngquant = require('imagemin-pngquant'); 
 
 
 gulp.task('imagemin', function () { 
    return gulp.src('./themes/theme_name/images/*') 
        .pipe(imagemin({ 
            progressive: true, 
            svgoPlugins: [{removeViewBox: false}], 
            use: [pngquant()] 
        })) 
        .pipe(gulp.dest('./themes/theme_name/images')); 
 }); 
 
 
  gulp.task('sass', function () { 
  gulp.src('./themes/theme_name/sass/**/*.scss') 
     .pipe(sourcemaps.init()) 
     .pipe(sass({outputStyle: 'compressed'}).on('error', sass.logError)) 
    .pipe(autoprefixer('last 2 version', 'safari 5', 'ie 7', 'ie 8', 'ie 9', 'opera 12.1', 'ios 6', 'android 4')) 
  .pipe(sourcemaps.write('./')) 
  .pipe(gulp.dest('./themes/theme_name/styles')); 
 }); 
 
 
 gulp.task('uglify', function() { 
 gulp.src('./themes/theme_name/lib/*.js') 
  .pipe(uglify('main.js')) 
  .pipe(gulp.dest('./themes/theme_name/scripts')) 
 }); 
 
 gulp.task('watch', function(){ 
    livereload.listen(); 
 
    gulp.watch('./themes/theme_name/sass/**/*.scss', ['sass']); 
    gulp.watch('./themes/theme_name/lib/*.js', ['uglify']); 
    gulp.watch(['./themes/theme_name/styles/style.css',   './themes/theme_name/**/*.twig', './themes/theme_name/scripts/*.js'], function (files){ 
    livereload.changed(files) 
  }); 
}); 

请您参考如下方法:

在您的工作目录中尝试这个 npm install -S gulp-livereload。可能您的 package.json 不包含此依赖项...