# 七.定义环境变量
# 1.安装
package.json
{
"name": "7.defineEnv",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"dev": "webpack-dev-server --open --mode development"
},
"keywords": [],
"author": "",
"license": "ISC",
"devDependencies": {
"html-webpack-plugin": "^3.2.0",
"webpack": "^4.29.6",
"webpack-cli": "^3.3.0",
"webpack-dev-server": "^3.2.1"
}
}
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# 2.文件
# 2.1 src/index.js
let url = ""
if (DEV === "dev") {
url = "http:localhost:3000"
} else {
url = "http:zhoubichuan.com"
}
console.log(url)
console.log(typeof FLAG)
console.log(EXPORESSION)
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# 2.2 index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<title>webpac定义环境变量</title>
</head>
<body></body>
</html>
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# 3.配置
webpack.config.js
const path = require("path")
let HtmlWebpackPlugin = require("html-webpack-plugin")
let webpack = require("webpack")
module.exports = {
mode: "development",
entry: {
home: "./src/index.js",
},
output: {
filename: "[name].js",
path: path.resolve(__dirname, "dist"),
},
plugins: [
new webpack.DefinePlugin({
// DEV: "'dev'"
DEV: JSON.stringify("production"),
FLAG: "true",
EXPORESSION: JSON.stringify("1+1"),
}),
new HtmlWebpackPlugin({
template: "./index.html",
filename: "index.html",
}),
],
}
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# 4.运行
npm run dev
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控制台打印我们所要的信息
http:zhoubichuan.com
boolean
1+1
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