webpack打包后const没有被转成var？

Question

项目webpack及babel依赖如下：

{
    "@babel/cli": "^7.2.0",
    "@babel/core": "^7.2.0",
    "@babel/polyfill": "^7.2.5",
    "@babel/preset-env": "^7.2.0",
    "webpack": "^4.28.4",
}

项目使用webpack4.x + babel7.x，但在编译后发现const没有被编译成var，导致IOS 9 Safari报错：

SyntaxError: Unexpected keyword 'const'. Const declarations are not supported in strict mode.

然后我将@babel/env配置成如下：

"presets": [
    [
      "@babel/env",
      {
        "useBuiltIns": "usage",
        "targets": {
          "chrome": 52,
          "browsers": ["last 2 versions", "safari 7"]
        },
        "loose": true
      }
    ]
  ],

仍然会报错，在网上查了错误 也没有具体的解决办法。。

请求各位大神支支招。。。。怎么哟

Answer 1

Const declarations are not supported in strict mode.

重点在strict mode严格模式
给@babel/preset-env的选项加上"modules": false试试

[
  "@babel/preset-env",
  {
    "useBuiltIns": "usage",
    "modules": false
  }
]