前端项目兼容IE11目标语法： es6 -> es5 api： promise、fetch等工具 babel7 @b

目标

语法： es6 -> es5
api： promise、fetch等

工具 babel7

@babel/preset-env 会根据浏览器环境引入polyfill 主要参数见下 useBuiltIns: "entry" | "usage" | "false", 默认false

"presets": [
    [
      "@babel/preset-env",
      {
        "useBuiltIns": "usage",
        "corejs": "3.7.0",
        "targets": {
          "browsers": [
            "last 2 versions",
            "ie >= 11"
          ]
        }
      }
    ],
    "@babel/preset-react",
    "@babel/preset-typescript"
  ]

插件: 箭头函数、Object.assign等

"plugins": [
    "@babel/plugin-transform-arrow-functions",
    "@babel/plugin-transform-object-assign",
    "@babel/plugin-transform-modules-commonjs",
    "@babel/plugin-transform-runtime"
]

fetch\promise

IE 11兼容fetch语法需要增加两个polyfill

Promise polyfill promise-polyfill
Fetch polyfill: whatwg-fetch A window.fetch JavaScript polyfill

import "promise-polyfill"
import "whatwg-fetch";

其他问题

有些库使用的es6 proxy（比如mobx5），babel是无法polyfill的，需要关注下

Due to the limitations of ES5, Proxies cannot be transpiled or polyfilled