Node.js-检查是否实际安装了模块 [英] Node.js - check if module is installed without actually requiring it

问题描述

在运行它之前，我需要检查是否已安装"mocha".我想出了以下代码:

I need to check whether "mocha" is installed, before running it. I came up with the following code:

try {
    var mocha = require("mocha");
} catch(e) {
    console.error(e.message);
    console.error("Mocha is probably not found. Try running `npm install mocha`.");
    process.exit(e.code);
}

我不喜欢这个例外的想法.有更好的方法吗?

I dont like the idea to catch an exception. Is there a better way?

推荐答案

您应使用require.resolve()而不是require().如果找到require将会加载库，但是require.resolve()不会加载，它将返回模块的文件名.

You should use require.resolve() instead of require(). require will load the library if found, but require.resolve() will not, it will return the file name of the module.

请参见 require.resolve文档

try {
    console.log(require.resolve("mocha"));
} catch(e) {
    console.error("Mocha is not found");
    process.exit(e.code);
}

如果找不到模块，则

require.resolve()确实会引发错误，因此您必须对其进行处理.

require.resolve() does throw error if module is not found so you have to handle it.

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