Grunt Babel Taking 6 Seconds Per File

问题

I'm trying to use Babel in my grunt build process to transpile my .js project files from ES6 to ES5. I have a watch task watching my .js directory for changes and when changes are detected, I run the babel task.

For some reason though, changing just one .js file takes anywhere between 6-10 seconds to complete. I have a feeling it's transpiling the entire project, but I'm not sure. My Gruntfile.js looks like this:

grunt.initConfig({
  watch: {
    babel: {
      files: ["<%= yeoman.app %>/scripts/**/*.js"],
      tasks: ["babel"]
    },
    livereload: {
      options: {
        livereload: LIVERELOAD_PORT
      },
      files: [
        "{.tmp,<%= yeoman.app %>}/scripts/**/*.js",
      ]
    }
  },
  babel: {
    options: {
      sourceMap: true,
      presets: ['es2015']
    },
    dist: {
      files: [
        {
          expand: true,
          cwd: '<%= yeoman.app %>/scripts/',
          src: ['**/*.js'],
          dest: '.tmp/scripts/'
        }
      ]
    }
  }
});
grunt.registerTask("serve", function(target) {
  return grunt.task.run(["watch"]);
});

When I run grunt serve and change a file it logs the execution time:

Running "babel:dist" (babel) task

Done, without errors.

Execution Time (2015-12-01 11:57:54 UTC) babel:dist 6.7s ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 100% Total 6.7s

But when I use babel-cli in my terminal, it transpiles in milliseconds, almost instantaneously even:

babel --presets es2015 script.js --out-file transpiled.js

Surely this is way too long. Am I doing something wrong here.

Any help is appreciated. Thanks in advance!

回答1:

During development you can decide to run the JS version of the Babel-core directly in the browser, which runs quite fast.

Then for deployment you can make a specific Grunt build task that removes the Babel-Core from the HTML and instead transpiles the files with the Grunt Babel plugin.

Your Gruntfile will have something like this:

grunt.registerTask('build', ['processhtml', 'babel']);
grunt.registerTask('default', [''watch']);

For the removal of the Babel-core JS you can use plugins like like grunt-processhtml: http://www.npmjs.com/package/grunt-processhtml . The HTML will look like this:

<!-- build:remove -->   
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/6.1.19/browser.min.js"></script>
<!-- /build -->

The JS Babel-core can found here: http://cdnjs.com/libraries/babel-core . You can download it and add it to your project or just run it from the CDN directly.

来源：https://stackoverflow.com/questions/34019931/grunt-babel-taking-6-seconds-per-file

标签

javascript

gruntjs

babeljs