本地环境下grunt操作报错

{
  "name": "webapp",
  "version": "1.0.0",
  "description": "This is a project set-up using Grunt to take case of some standard tasks such as: compiling AMD based modules using RequireJS, watching/compiling Sass into CSS, watching/linting JS code and some other things such as running unit tests",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [
    "Grunt"
  ],
  "author": "***",
  "license": "ISC",
  "devDependencies": {
    "grunt": "^0.4.5",
    "grunt-autoprefixer": "^3.0.3",
    "grunt-contrib-clean": "^0.7.0",
    "grunt-contrib-concat": "^0.5.1",
    "grunt-contrib-copy": "^0.8.2",
    "grunt-contrib-cssmin": "^0.14.0",
    "grunt-contrib-jshint": "^0.11.3",
    "grunt-contrib-uglify": "^0.11.0",
    "grunt-contrib-watch": "^0.6.1"
  }
}

module.exports = function (grunt) {
  // 项目配置
  grunt.initConfig({
    pkg: grunt.file.readJSON('package.json'),
    jshint:{
        files:['Gruntfile.js','js/*.js'],
        options:{
            curly:true, 
            eqeqeq:true,
            immed:true,
            newcap:true,
            noarg:true,
            undef:true,
            boss:false,
            eqnull:true,
            browser:true,
            expr:true,
            noempty:true,
            regexp:true,
            devel:true,
            node:true
        }
    },
    uglify: {
      options: {
        banner: '/*! <%= pkg.name %> <%= grunt.template.today("yyyy-mm-dd") %> */\n'
      },
      build: {
        src: 'js/concated.js',
        dest: 'js/uglify.min.js'
      }
    },
    concat: {
      options: {
        separator: ';'
      },
      dist: {
        src: [ 'js/*.js' ],
        dest: 'js/concated.js'
      }
    },
    copy: {
      build: {
        cwd: 'js/',
        src: '*.js',
        dest: 'js2/',
        expand: true
      },
    },
    clean: {
      build: {
        src: 'js/*.html'
      },
    },
    // 给CSS3属性添加前缀插件,使用的autoprefixer输出的文件和读取的文件在同一个目录中。
    autoprefixer: {
      build: {
        expand: true,
        cwd: 'css/',
        src: '*.css',
        dest: 'css/'
      }
    },
    // 将CSS文件压缩，并将多个文件合并成一个单一的文件。
    cssmin: {
      build: {
        files: {
          'css/cssmin.min.css': [ 'css/*.css' ]
        }
      }
    },
    watch: {
      js: {
        files: [ 'js/*.js' ],
        tasks: [ 'uglify','copy' ]
      },
      css: {
        files: [ 'css/*.css' ],
        tasks: [ 'autoprefixer','cssmin' ]
      }
    }
  });
  // 加载提供任务的插件
  grunt.loadNpmTasks('grunt-contrib-jshint');
  grunt.loadNpmTasks('grunt-contrib-copy');
  grunt.loadNpmTask('grunt-autoprefixer');
  grunt.loadNpmTasks('grunt-contrib-concat');
  grunt.loadNpmTasks('grunt-contrib-uglify');
  grunt.loadNpmTasks('grunt-contrib-cssmin');
  grunt.loadNpmTasks('grunt-contrib-clean');
  grunt.loadNpmTasks('grunt-contrib-watch');
  // 默认任务
  grunt.registerTask(
  'default', ['jshint', 'copy', 'concat', 'uglify', 'watch']);
}

以上是package.json和Gruntfile.js文件的配置以及目录结构；
操作命令grunt时，为什么报以下错误？

---

task 里面，没有default任务。

---

试试安装grunt-cli。
npm install grunt-cli -g

---

可能大家没有注意到，报的错误是 grunt.loadNpmTask is not a function，仔细看你的代码，有一行 grunt.loadNpmTask('grunt-autoprefixer')，这一行报错了，少了个 s。