[英]browser throw error of export/import keyword even webpack and babel is installed
我正在使用核心javascript和html开发一个非常基本和简单的应用程序,我已经安装了webpack v 4并使用以下命令启动服务器
npm run webpack
项目编译成功; 下面是输出
> canvas@1.0.0 webpack /opt/parixan/canvas
> webpack-dev-server --inline --hot
ℹ 「wds」: Project is running at http://localhost:8080/
ℹ 「wds」: webpack output is served from /
ℹ 「wdm」: Hash: 99985e9b8632c783a375
Version: webpack 4.12.1
Time: 819ms
Built at: 2018-06-30 18:45:48
Asset Size Chunks Chunk Names
bundle.js 354 KiB main [emitted] main
bundle.js.map 406 KiB main [emitted] main
Entrypoint main = bundle.js bundle.js.map
[./js/color.js] 359 bytes {main} [built]
[./js/index.js] 628 bytes {main} [built]
[./node_modules/loglevel/lib/loglevel.js] 7.68 KiB {main} [built]
[./node_modules/sockjs-client/dist/sockjs.js] 176 KiB {main} [built]
[./node_modules/url/url.js] 22.8 KiB {main} [built]
[./node_modules/webpack-dev-server/client/index.js?http://localhost:8080] (webpack)-dev-server/client?http://localhost:8080 7.75 KiB {main} [built]
[./node_modules/webpack-dev-server/client/overlay.js] (webpack)-dev-server/client/overlay.js 3.58 KiB {main} [built]
[./node_modules/webpack-dev-server/client/socket.js] (webpack)-dev-server/client/socket.js 1.05 KiB {main} [built]
[./node_modules/webpack-dev-server/node_modules/strip-ansi/index.js] (webpack)-dev-server/node_modules/strip-ansi/index.js 161 bytes {main} [built]
[0] multi (webpack)-dev-server/client?http://localhost:8080 webpack/hot/dev-server ./js/index.js 52 bytes {main} [built]
[./node_modules/webpack/hot sync ^\.\/log$] (webpack)/hot sync nonrecursive ^\.\/log$ 170 bytes {main} [built]
[./node_modules/webpack/hot/dev-server.js] (webpack)/hot/dev-server.js 1.6 KiB {main} [built]
[./node_modules/webpack/hot/emitter.js] (webpack)/hot/emitter.js 77 bytes {main} [built]
[./node_modules/webpack/hot/log-apply-result.js] (webpack)/hot/log-apply-result.js 1.27 KiB {main} [built]
[./node_modules/webpack/hot/log.js] (webpack)/hot/log.js 1010 bytes {main} [built]
+ 14 hidden modules
ℹ 「wdm」: Compiled successfully.
但是当我导航到localhost:8080 / alphabet.html时,它将在控制台中引发错误
未捕获到的SyntaxError:意外的令牌导出。 Alphabet.js:30
我也注意到有build文件夹下没有bundle.js文件作为webpack.config.js提到
这是我的文件夹结构
├── README.md
├── alphabet.css
├── alphabet.html
├── build
├── fruits
├── js
├── alphabet.js
├── color.js
└── index.js
├── .babelrc
├── package.json
└── webpack.config.js
{
"presets": ["@babel/preset-env"]
}
"scripts": {
"webpack": "webpack-dev-server --inline --hot",
"start": "http-server"
},
"main": "./js.index.js",
"devDependencies": {
"@babel/core": "^7.0.0-beta.51",
"babel-loader": "^8.0.0-beta.4",
"babel-register": "^6.26.0",
"jsxobj": "^1.1.0",
"webpack": "^4.12.1",
"webpack-cli": "^3.0.8",
"webpack-dev-server": "^3.1.4",
"webpack-node-externals": "^1.7.2"
},
"dependencies": {
"@babel/preset-env": "^7.0.0-beta.51",
"babel-eslint": "^7.2.3",
"babel-preset-es2015": "^6.24.1",
"path": "^0.12.7"
}
module.exports = {
context: __dirname,
entry: "./js/index.js",
mode: "development",
output: {
path: __dirname + "/build",
filename: "bundle.js"
},
module: {
rules: [
{
test: /\.js$/,
exclude: /(node_modules|bower_components)/,
use: {
loader: "babel-loader",
options: {
presets: ["@babel/preset-env"]
}
}
}
]
},
devtool: "source-map",
resolve: {
extensions: [".html", ".js", ".json", ".css"]
}
};
import { fetchImage } from "./alphabet.js";
import { color } from "./color.js";
const colorBox = color;
console.log("colorBox", colorBox);
const len = Object.keys(colorBox).length;
fetchImage(colorBox);
export const fetchImage = letter => {
const fruit = fruits[letter] || "tamarindo";
const request = new Request(`./fruits/${fruit}.png`, myInit);
fetch(request)
.then(response => response.blob())
.then(blob => {
const objectURL = URL.createObjectURL(blob);
const img = new Image(200);
img.src = objectURL;
let element = document.getElementById("figure");
while (element.firstChild) {
element.removeChild(element.firstChild);
}
element.appendChild(img);
});
};
我对这个Alphabet.html文件的主要怀疑
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Alphabet</title>
<link rel="stylesheet" href="./alphabet.css">
</head>
<body>
<div class="content" >
<section class="alphabet"></section>
<figure id="figure"></figure>
</div>
<script src="./js/alphabet.js"></script>
</body>
</html>
如果我更改<script src="./js/index.js">
比它抛出错误
未捕获到的SyntaxError:意外令牌{
即导入和导出关键字无法识别
如何解决这个问题呢?
如果您的目标是启用使用import
和export
语句,则应在脚本标签上使用module
类型:
<script type="module" ... />
不支持此功能的旧版浏览器会忽略此设置,这意味着您可以确保旧版浏览器甚至不尝试解析它。 为了确保较新的浏览器不会解析旧代码,可以使用nomodule
:
<script type="text/javascript" nomodule ... />
有关使用<script>
标记的更多信息,请参见MDN文档,例如: https : //developer.mozilla.org/en-US/docs/Web/HTML/Element/script
1:webpack-dev-server将捆绑包直接构建到内存中,这就是为什么最好使用html-webpack-plugin,因此将捆绑包自动地插入到html中的原因。
2:之所以收到此错误,是因为您引用的是es6文件,而不是实际的软件包。 这可能不适用于所有浏览器。
要使用html-webpack-plugin
只需将其添加到您的构建中即可。 附言:这希望您有一个基本的html,它将插入资产。
https://github.com/jantimon/html-webpack-plugin
plugins: [
new HtmlWebpackPlugin({
template: 'path/to/my/index.html'
})
]
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