javascript - Check if a node.js module is available

Question

I'm looking for a way to find out if a module is available.

For example, I want to check if the module mongodb is available, programmatically.

Also, it shouldn't halt the program if a module isn't found, I want to handle this myself.

_{PS: I added this question because Google isn't helpful.}

Answer 1

如果您只想检查模块是否可用（但如果不可用则不加载它），还有一种更聪明的方法：

function moduleAvailable(name) {
    try {
        require.resolve(name);
        return true;
    } catch(e){}
    return false;
}

if (moduleAvailable('mongodb')) {
    // yeah we've got it!
}

Answer 2

Here is the most clever way I found to do this. If anyone has a better way to do so, please point it out.

var mongodb;
try {
    mongodb = require( 'mongodb' );
}
catch( e ) {
    if ( e.code === 'MODULE_NOT_FOUND' ) {
        // The module hasn't been found
    }
}

Answer 3

也许resolve-like 模块在这里会有所帮助？

模块的数量存在于 npm 上：

• 异步解析
• 解决
• 解决它
• 增强分辨率
• 定位器

我先写了，async-resolve例如：

var Resolver = require('async-resolve');
var resolver_obj = new Resolver();
resolver_obj.resolve('module', __dirname, function(err, filename) {
  return console.log(filename);
});

它使用node模块路径解析规则，但不会像node它那样阻塞主循环。结果你得到文件名，所以它可以用来决定它的本地模块或全局和其他东西。

Answer 4

带有 1 行代码的 ES6 简单解决方案：

const path = require('path');
const fs = require('fs');

function hasDependency(dep) {
        return module.paths.some(modulesPath => fs.existsSync(path.join(modulesPath, dep)));
}

Answer 5

使用 ES6 箭头函数

var modulePath = m => { try { return require.resolve(m) } catch(e) { return false } }