如果使用 JavaScript、或者曾经与 JavaScript 项目、Node.js 或前端项目进行过交互,则肯定会遇到过 package.json 文件。
它有什么用途?应该了解它的什么,可以使用它完成哪些有趣的事情?
package.json 文件是项目的清单。 它可以做很多完全互不相关的事情。 例如,它是用于工具的配置中心。 它也是 npm 和 yarn 存储所有已安装软件包的名称和版本的地方。

文件结构

这是一个示例的 package.json 文件:

{}

它是空的! 对于应用程序,package.json 文件中的内容没有固定的要求。 唯一的要求是必须遵守 JSON 格式,否则,尝试以编程的方式访问其属性的程序则无法读取它。
如果要构建要在 npm 上分发的 Node.js 软件包,则必须具有一组可帮助其他人使用它的属性。 稍后会详细介绍。

这是另一个 package.json:

{
  "name": "nodejs_cn"
}

它定义了 name 属性,用于告知应用程序或软件包的名称。

这是一个更复杂的示例,该示例是从 Vue.js 应用程序示例中提取的:

{
  "name": "test-project",
  "version": "1.0.0",
  "description": "A Vue.js project",
  "main": "src/main.js",
  "private": true,
  "scripts": {
    "dev": "webpack-dev-server --inline --progress --config build/webpack.dev.conf.js",
    "start": "npm run dev",
    "unit": "jest --config test/unit/jest.conf.js --coverage",
    "test": "npm run unit",
    "lint": "eslint --ext .js,.vue src test/unit",
    "build": "node build/build.js"
   },
   "dependencies": {
      "vue": "^2.5.2"
   },
   "devDependencies": {
     "autoprefixer": "^7.1.2",
     "babel-core": "^6.22.1",
     "babel-eslint": "^8.2.1",
     "babel-helper-vue-jsx-merge-props": "^2.0.3",
     "babel-jest": "^21.0.2",
     "babel-loader": "^7.1.1",
     "babel-plugin-dynamic-import-node": "^1.2.0",
     "babel-plugin-syntax-jsx": "^6.18.0",
     "babel-plugin-transform-es2015-modules-commonjs": "^6.26.0",
     "babel-plugin-transform-runtime": "^6.22.0",
     "babel-plugin-transform-vue-jsx": "^3.5.0",
     "babel-preset-env": "^1.3.2",
     "babel-preset-stage-2": "^6.22.0",
     "chalk": "^2.0.1",
     "copy-webpack-plugin": "^4.0.1",
     "css-loader": "^0.28.0",
     "eslint": "^4.15.0",
     "eslint-config-airbnb-base": "^11.3.0",
     "eslint-friendly-formatter": "^3.0.0",
     "eslint-import-resolver-webpack": "^0.8.3",
     "eslint-loader": "^1.7.1",
     "eslint-plugin-import": "^2.7.0",
     "eslint-plugin-vue": "^4.0.0",
     "extract-text-webpack-plugin": "^3.0.0",
     "file-loader": "^1.1.4",
     "friendly-errors-webpack-plugin": "^1.6.1",
     "html-webpack-plugin": "^2.30.1",
     "jest": "^22.0.4",
     "jest-serializer-vue": "^0.3.0",
     "node-notifier": "^5.1.2",
     "optimize-css-assets-webpack-plugin": "^3.2.0",
     "ora": "^1.2.0",
     "portfinder": "^1.0.13",
     "postcss-import": "^11.0.0",
     "postcss-loader": "^2.0.8",
     "postcss-url": "^7.2.1",
     "rimraf": "^2.6.0",
     "semver": "^5.3.0",
     "shelljs": "^0.7.6",
     "uglifyjs-webpack-plugin": "^1.1.1",
     "url-loader": "^0.5.8",
     "vue-jest": "^1.0.2",
     "vue-loader": "^13.3.0",
     "vue-style-loader": "^3.0.1",
     "vue-template-compiler": "^2.5.2",
     "webpack": "^3.6.0",
     "webpack-bundle-analyzer": "^2.9.0",
     "webpack-dev-server": "^2.9.1",
     "webpack-merge": "^4.1.0"
   },
   "engines": {
     "node": ">= 6.0.0",
     "npm": ">= 3.0.0"
   },
   "browserslist": ["> 1%", "last 2 versions", "not ie <= 8"]
}