解决jest处理es模块示例详解

目录

• 问题场景
• 解决方法

问题场景

项目使用jest进行测试时, 当引入外部库是es模块时, jest无法处理导致报错.

Test suite failed to run
    Jest encountered an unexpected token
    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.
    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".
    Here's what you can do:
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.
Details:
/home/xueyou/workspace/projects/node_modules/lodash-es/lodash.js:10
import * as lodash from 'lodash-es'
SyntaxError: Unexpected token *

解决方法

查阅issues发现, 目前jest不支持em模块, 只有通过babel去处理了

安装依赖

yarn add --dev babel-jest @babel/core @babel/preset-env babel-plugin-transform-es2015-modules-commonjs

配置babel.config.js

module.exports = {
    presets: [
        [
            "@babel/preset-env",
            {
                targets: {
                    node: "current"
                }
            }
        ]
    ],
    plugins: ["transform-es2015-modules-commonjs"]
};

配置jest.config.js

module.exports = {
    preset: "ts-jest",
    testMatch: ["<rootDir>/tests/**/*.(spec|test).ts?(x)"],
    transform: {
        // 将.js后缀的文件使用babel-jest处理
        "^.+\\.js$": "babel-jest",
        "^.+\\.(ts|tsx)$": "ts-jest"
    },
    // 下面非要从重要, 将不忽略 lodash-es, other-es-lib 这些es库, 从而使babel-jest去处理它们
    transformIgnorePatterns: ["<rootDir>/node_modules/(?!(lodash-es|other-es-lib))"]
};

脚注

• Unexpected import inside nodejs module
• Unexpected Token Import for ES6 modules

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