ESLint的简单使用（js,ts,vue）

一、ESLint介绍

1.为什么要用ESLint

统一团队编码规范（命名，格式等）

统一语法

减少git不必要的提交

减少低级错误

在编译时检查语法，而不是等js引擎运行时才检查

2.eslint用法

可以手动下载配置

可以通过vue脚手架创建项目时自动下载

3.ESLint包

安装方式：

通过npm直接进行全局安装npm i eslint -D

通过vue脚手架创建项目时选择安装eslint模块包vue create 创建项目时选择eslint安装的包

vscode中ESLint扩展工具

二、手动下载配置(js)

1.创建一个测试文件夹：eslint-test

2.初始化项目：npm init -y(创建package.json)

3.直接在项目中安装eslint包npm i eslint -D

node_modules中下载了很多包，.bin/eslint.cmd脚本文件，内部通过nodejs执行eslint运行包的代码；@eslint包用来规范eslint配置文件；eslint开头的包是eslint运行包，包含eslint代码。

4.生成ESLint配置文件

创建eslint.config.js文件

export default {rules: {"no-unused-vars": "error","no-console": "error","no-sparse-arrays": "error","no-undef": "error","no-unreachable": "error","no-dupe-keys": "error"}
}

在package.json文件中添加type属性，添加命令 

{"name": "eslint-test","version": "1.0.0","main": "index.js","type": "module","scripts": {"lint": "eslint ."},"keywords": [],"author": "","license": "ISC","description": "","dependencies": {"eslint": "9.14.0"}
}

 创建js文件src/index.js

//不允许变量声明但没有使用no-unused-vars
const name = 'zs'//不允许打印no-console
console.log('name');//不允许数组中有空元素no-sparse-arrays
const arr = [1, , 3]//不允许有未声明的变量no-undef
console.log(afffffff);//不允许函数return后还有代码no-unreachable
function showFn(toName, fromName) {let a = 0;return a;a = 1
}//不允许对象有重复的key,no-dupe-keys
const obj = {name: 'zs',name: 'zs1'
}

 终端执行命令npm run lint规范代码

---

ESLint可以创建独立的配置文件.eslintrc.js，也可以直接在package.json中配置

a.执行node_modules/.bin文件夹里的eslint脚本来创建配置文件

包含完整脚本路径的命令：'./node_modules/.bin/eslint --init'

也可以用npx来执行npxeslint --init

创建配置文件过程中，需要选择配置

 自动生成eslint.config.mjs文件

eslint.config.mjs
import globals from "globals";
import pluginJs from "@eslint/js";/** @type {import('eslint').Linter.Config[]} */
export default [{files: ["**/*.js"], languageOptions: {sourceType: "commonjs"}},{languageOptions: { globals: globals.browser }},pluginJs.configs.recommended,
];

创建js文件，输入npx eslint 文件名执行语法检查

5.规范集简化配置npm i@eslint/js

// export default {
//     rules: {
//         "no-unused-vars": "error",
//         "no-console": "error",
//         "no-sparse-arrays": "error",
//         "no-undef": "error",
//         "no-unreachable": "error",
//         "no-dupe-keys": "error"
//     }
// }
//规则集
import js from '@eslint/js'
export default [js.configs.recommended]

三、手动安装eslint(ts)

1.创建一个测试文件夹：eslint-ts-test

2.初始化项目：npm init -y(创建package.json)

3.直接在项目中安装eslint包npm i eslint @eslint/js @typescript-eslint/parser -D

{"name": "pro","version": "1.0.0","main": "index.js","type": "module","scripts": {"lint": "eslint ."},"keywords": [],"author": "","license": "ISC","description": "","devDependencies": {"@eslint/js": "9.14.0","eslint": "9.14.0","@typescript-eslint/parser": "8.14.0"}
}

 4.新建配置文件eslint.config.js文件

import tsPsrser from '@typescript-eslint/parser'export default {//文件配置，哪些文件需要被校验,忽略eslint.config.js文件ignores: ["eslint.config.js"],files: ["**/*.ts"],//规范配置rules: {"no-unused-vars": "error","no-console": "error"},//语言配置languageOptions: {//指定解析器parser: tsPsrser}
}

 5.创建ts文件，src/index.ts

const age=18
console.log(name)/*ts类型定义
*ts相关的校验，eslint自带的校验espress解析器无法识别
*我们需要ts解析器来解析ts代码，完成类型校验
*/
interface Uesr{name:string;age:number;
}

  Parsing error: The keyword 'interface' is reserved

ts相关的校验，eslint自带的校验espress解析器无法识别

我们需要ts解析器来解析ts代码，完成类型校验 npm i @typescript-eslint/parser

四、手动安装eslint(vue)

1.创建一个测试文件夹：eslint-ts-test

2.初始化项目：npm init -y(创建package.json)

3.直接在项目中安装eslint包npm i eslint @eslint/js @typescript-eslint/parser vue-eslint-parser -D

{"name": "eslint-test","version": "1.0.0","main": "index.js","type": "module","scripts": {"lint": "eslint ."},"keywords": [],"author": "","license": "ISC","description": "","dependencies": {"@eslint/js": "9.14.0","@typescript-eslint/parser": "8.14.0","eslint": "9.14.0","vue-eslint-parser": "9.4.3"}
}

 4.新建配置文件eslint.config.js文件

import tsParser from '@typescript-eslint/parser'
import vueParser from 'vue-eslint-parser'
export default {ignores: ["eslint.config.js"],files: ["**/*.ts", "**/*.vue"],rules: {"no-unused-vars": "error","no-console": "error","no-sparse-arrays": "error","no-undef": "error","no-unreachable": "error","no-dupe-keys": "error"},languageOptions: {//指定解析器parser: vueParser,//解析器的语法parser设置parserOptions: {parser: tsParser}}
}

 5.创建vue文件，src/index.vue

<template></template>
<script setup lang="ts">
//不允许变量声明但没有使用no-unused-vars
const name = 'zs'//不允许打印no-console
console.log('name');//不允许数组中有空元素no-sparse-arrays
const arr = [1, , 3]//不允许有未声明的变量no-undef
console.log(afffffff);//不允许函数return后还有代码no-unreachable
function showFn(toName, fromName) {let a = 0;return a;a = 1
}//不允许对象有重复的key,no-dupe-keys
const obj = {name: 'zs',name: 'zs1'
}//类型定义
interface User{name:string;age:number;
}
</script>

五、自定义插件

 1.rule定义

针对这个规范的需求，编写一个rule，原理是通过ast节点处理来完成

//规则的本质是一个对象，
//eslint插件，必须长得像一个约定好的对象
export const noMiaomiVars = {//插件的元信息meta: {messages: {noMiaomiVars: "不允许使用miaomi变量"}},create(context) {return {//  这是一个访问者模式，访问到某一个ast的节点，就进行处理VariableDeclaration(node) {console.log('VariableDeclaration', node);},VariableDeclarator(node) {console.log('VariableDeclarator', node);},Identifier(node) {console.log('Identifier', node);if (node.name == 'miaomi') {context.report({node,messageId: 'noMiaomiVars',data: {name: node.name}})}},Literal(node) {console.log('Identifier', node);}}}
}

2.plugin插件定义

将rule进行插件化，提供给外部使用‘

import { noMiaomiVars } from '../rules/no-miaomi-vars.js'
export const eslintMiaomiPlugin = {rules: {"no-miaomi-vars": noMiaomiVars}
}

3.use将插件引入到eslint配置文件中，使用插件

import tsParser from '@typescript-eslint/parser'
import vueParser from 'vue-eslint-parser'
import { eslintMiaomiPlugin } from './eslint/plugins/eslint-plugin-miaomi.js'
export default {ignores: ["eslint.config.js"],files: ["src/**/*.js", "**/*.ts", "**/*.vue"],plugins: {miaomi: eslintMiaomiPlugin //插件定义好后，插件名称就是规则的作用域},rules: {"miaomi/no-miaomi-vars": "error",},languageOptions: {//指定解析器parser: vueParser,//解析器的语法parser设置parserOptions: {parser: tsParser}}
}