Question

我关注Get To Know Babel The JavaScript Compiler Tutorial，这是我的polygon.js

class Polygon {  
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }

  getArea() {
    return this.calcArea()
  }

  calcArea() {
    return this.height * this.width;
  }
}

我跑

babel polygon.js -o output.js
cat output.js | pbcopy

粘贴：

class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }

  getArea() {
    return this.calcArea();
  }

  calcArea() {
    return this.height * this.width;
  }
}

我期待转向ES5，但代码保持不变。

发生了什么？

$ .babel --version
6.2.0 (babel-core 6.2.1)

编辑：我使用npm install babel-preset-2015 -g

安装了预设

~/es6:.babel polygon.js -o output.js --presets es2015
Error: Couldn't find preset "es2015" relative to directory "."
    at OptionManager.mergePresets (/usr/local/lib/node_modules/babel-cli/node_modules/babel-core/lib/transformation/file/options/option-manager.js:327:17)
    at OptionManager.mergeOptions (/usr/local/lib/node_modules/babel-cli/node_modules/babel-core/lib/transformation/file/options/option-manager.js:287:12)
    at OptionManager.init (/usr/local/lib/node_modules/babel-cli/node_modules/babel-core/lib/transformation/file/options/option-manager.js:416:10)
    at File.initOptions (/usr/local/lib/node_modules/babel-cli/node_modules/babel-core/lib/transformation/file/index.js:190:75)
    at new File (/usr/local/lib/node_modules/babel-cli/node_modules/babel-core/lib/transformation/file/index.js:121:22)
    at Pipeline.transform (/usr/local/lib/node_modules/babel-cli/node_modules/babel-core/lib/transformation/pipeline.js:42:16)
    at transform (/usr/local/lib/node_modules/babel-cli/lib/babel/util.js:53:22)
    at Object.compile (/usr/local/lib/node_modules/babel-cli/lib/babel/util.js:62:12)
    at /usr/local/lib/node_modules/babel-cli/lib/babel/file.js:130:23
    at arrayEach (/usr/local/lib/node_modules/babel-cli/node_modules/lodash/index.js:1289:13)

编辑：安装后问题是-g。我在本地安装并且可以正常工作。

Answer 1

这也引起了我的注意。新版本的Babel要求您安装预设，可能是http://ideone.com/xR1v0j，并在CLI命令中明确指定。

根据Babel的安装位置（全局/本地），您需要安装预设位置：

npm install babel-preset-es2015

然后你可以运行Babel。例如，这会使用预设将一个文件夹中的所有文件转换为另一个文件夹。

babel [srcFolder] --out-dir [outFolder] --presets es2015

Babel对我的Javascript没有影响

1 个答案: