未启用可选链接 React Native答案

【问题标题】：Optional Chaining not enabled ReactNative未启用可选链接 React Native
【发布时间】：2019-03-07 05:35:28
【问题描述】：

在 react react native 中运行 android 项目时出现此错误。

这是全新安装的 react native 版本 "react": "^16.3.1","react-native": "^0.57.1",

它给出了可选链接的错误。谁能帮助我如何在本机反应中启用可选链接。

Loading dependency graph, done.
BUNDLE [android, dev] ....../index.js ▓▓▓▓▓▓▓▓▓▓░░░░░░ 64.3% (667/832)::ffff:127.0.0.1 - - [02/Oct/2018:04:30:46 +0000] "GET /index.delta?platform=android&dev=true&minify=false HTTP/1.1" 500 - "-" "okhttp/3.10.0"
error: bundling failed: SyntaxError: C:\ReactNative\mrn\node_modules\react-native\Libraries\Components\Switch\Switch.js: Support for the experimental syntax 'optionalChaining' isn't currently enabled (103:41):

101 | // Support deprecated color props.
102 | let _thumbColor = thumbColor;

103 | let _trackColorForFalse = trackColor?.false;
| ^
104 | let _trackColorForTrue = trackColor?.true;
105 |
106 | // TODO: Remove support for these props after a couple releases.

Add @babel/plugin-proposal-optional-chaining (https://git.io/vb4Sk) to the 'plugins' section of your Babel config to enable transformation.
at _class.raise (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:3939:15)
at _class.expectPlugin (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:5253:18)
at _class.parseSubscript (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:5959:12)
at _class.parseSubscript (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:2716:51)
at _class.parseSubscripts (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:5944:19)
at _class.parseSubscripts (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:2669:52)
at _class.parseExprSubscripts (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:5934:17)
at _class.parseMaybeUnary (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:5903:21)
at _class.parseExprOps (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:5812:21)
at _class.parseMaybeConditional (C:\ReactNative\mrn\node_modules@babel\parser\lib\index.js:5784:21)
BUNDLE [android, dev] ....../index.js ▓▓▓▓▓▓▓▓▓▓▓▓░░░░ 77.5% (752/854), failed.

【问题讨论】：

标签： react-native babeljs optional-chaining

【解决方案1】：

我通过在根目录中添加文件 .babelrc 文件来修复它

{
  "plugins": [
    "@babel/plugin-proposal-optional-chaining"
  ],
  "presets": [
    "react-native"
  ]
}

修改.babelrc文件后重启metro

【讨论】：

【解决方案2】：

错误说要添加@babel/plugin-proposal-optional-chaining

尝试安装this

npm install --save-dev @babel/plugin-proposal-optional-chaining

【讨论】：

已安装但未启用
尝试将 { "plugins": ["@babel/plugin-proposal-optional-chaining"]} 添加到您的 .babelrc 或运行 babel --plugins @babel/plugin-proposal-optional-chaining script.js

【解决方案3】：

在将我的应用程序从旧的 react-native 版本升级到新版本后，我也遇到了这个问题。它需要 devDependencies 中的一些 babel 库。这是我尝试过的 devDependencies

“devDependencies”：{ "babel-jest": "23.6.0", “笑话”：“23.6.0”， “metro-react-native-babel-preset”：“0.50.0”， “反应测试渲染器”：“16.6.1”}，“开玩笑”：{ “预设”：“反应原生”}

【讨论】：