背景：项目打包后，发现vendor.js不算大，而vendor.js.map很大，导致发布生产环境文件超限制

 static/js/vendor.5b2373a0266a53420600.js     715 kB       0  [emitted]  [big]  vendor
 static/js/vendor.5b2373a0266a53420600.js.map     4.4 MB       0  [emitted]         vendor
下面介绍打包如果不出现.js.map文件，及.js.map作用
1.在项目下进入目录：项目包/config/index.js

找到productionSourceMap
     * Source Maps
    productionSourceMap: true,
    // https://webpack.js.org/configuration/devtool/#production
    devtool: '#source-map',
2.将productionSourceMap的true改为false即可
    productionSourceMap: false,
    // https://webpack.js.org/configuration/devtool/#production
    devtool: '#source-map',
3.打生产包:npm run build
Hash: 450e46e5a578d8ed5832
Version: webpack 3.12.0
Time: 19211ms
                                              Asset       Size  Chunks                    Chunk Names
                static/js/2.f45baf9afd59da355a2c.js    17.9 kB       2  [emitted]
                 static/img/healthIcon2.0a76940.png    21.7 kB          [emitted]
                 static/img/healthIcon1.7f9e278.png      21 kB          [emitted]
                 static/img/healthIcon3.a2530d6.png    20.3 kB          [emitted]
                static/js/0.2623d3f24b6cb900e249.js     182 kB       0  [emitted]
                static/js/1.68a7b37dd5366d3385bc.js    62.6 kB       1  [emitted]
                 static/img/healthIcon4.42cd92c.png    18.9 kB          [emitted]
                static/js/3.dd658b712540b545b1a8.js    6.57 kB       3  [emitted]
           static/js/vendor.ed30b6e3d0cfb8529feb.js     962 kB       4  [emitted]  [big]  vendor
              static/js/app.ab727f325a694968cc20.js    1.22 kB       5  [emitted]         app
         static/js/manifest.bad9ce278a16a20c8817.js    1.48 kB       6  [emitted]         manifest
static/css/app.e93cb55eadaef6e12f4bccfcc6e2e3cc.css    35.6 kB       5  [emitted]         app
                                         index.html  555 bytes          [emitted]
  Build complete.
  Tip: built files are meant to be served over an HTTP server.