巨应打字员


快速掌握如何在 NodeJs 中定义模块

---

## 定义模块

### 方式一

```js
//moduleClass.js
//导出一个类
module.exports = class classModule {
  constructor(para) {
    this.para = para;
  }

  test() {
    return this.para + 2;
  }
};
```

### 方式二

```js
//moduleExample.js
//使用exports
const tmpData = "+私有变量+";

exports.testa = (r) => console.log("testA执行" + tmpData + r);

exports.testb = (r) => console.log("testB执行" + tmpData + r);
```

### 事件

```js
//moduleEvent.js
const EventEmitter = require("events");

module.exports = new EventEmitter();

//一秒后触发事件
setTimeout(() => {
  module.exports.emit("ready");
}, 1000);
```

## 导入模块

```js
const classModule = require("./moduleClass");
const eventModule = require("./moduleEvent");
const example = require("./moduleExample");

var tmpClass = new classModule(1);
console.log("classModule.test():" + tmpClass.test());

eventModule.on("ready", () => {
  console.log("ready事件触发了");
});

example.testa(1);
example.testb(2);
```

输出

```
classModule.test():3
testA执行+私有变量+1
testB执行+私有变量+2
ready事件触发了
```

## 源码下载

https://github.com/MscoderStudio/nodejs-tutorials/tree/master/module_example

## 官方文档

https://nodejs.org/dist/latest-v10.x/docs/api/modules.html#modules_exports


NodeJS 模块


### 1.首先安装这个库

https://www.npmjs.com/package/recursive-readdir

### 2.代码：

```js
const util = require("util");
const recursive = require("recursive-readdir");
const readdirAsync = util.promisify(recursive);
const statAsync = util.promisify(fs.stat);

const files = await readdirAsync(basepath);
const stats = await Promise.all(
  files.map((filename) =>
    statAsync(filename).then((stat) => ({
      filename,
      stat,
    }))
  )
);
const sortedFiles = stats
  .sort((a, b) => a.stat.mtime.getTime() - b.stat.mtime.getTime())
  .map((stat) => stat.filename);

console.log(sortedFiles);
```


Nodejs 递归获取所有文件并按时间排序

### 1.require.main.filename

```js
var path = require("path");
var appDir = path.dirname(require.main.filename);
```

### 2.global.X

```js
// index.js
var path = require("path");
global.appRoot = path.resolve(__dirname);

// lib/moduleA/component1.js
require(appRoot + "/lib/moduleB/component2.js");
```

### 3.process.cwd（）

```shell
$ cd /home/demo/
$ mkdir subdir
$ echo "console.log(process.cwd());" > subdir/demo.js
$ node subdir/demo.js
/home/demo
$ cd subdir
$ node demo.js
/home/demo/subdir
```

### 4.app-root-path

使用该包 https://github.com/inxilpro/node-app-root-path



NodeJs 获取程序根目录的几种方式

实战演练：一步一步的教你 nodejs 怎么引用 c++写的动态链接库
环境：win10+vscode+vs2017+node10

---

## 1. 新建 c++动态链接库

定义一个非常简单的库（因为我不是专业的 c++程序员，复杂的不会写~）

```cpp
--------------sdk.h

#pragma once
#include<string>

class sdk
{
public:
	static __declspec(dllexport) void Test(char* string);
};


---------------sdk.cpp
#include "stdafx.h"
#include "sdk.h"

void  sdk::Test(char* string)
{
	strcpy_s(string, 100, "hello world");
}
```

## 2. 新建 c++扩展项目 myaddon

首先引用依赖项

npm i bindings --save

npm i node-addon-api --save

代码：

```js
-----------------index.js;
var addon = require("bindings")("sdkaddon");

console.log(addon.test());
```

```json
-------------------package.json
{
  "name": "myaddon",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "bindings": "^1.3.1",
    "node-addon-api": "^1.6.2"
  }
}


-------------------------sdkaddon.cc
#include <napi.h>
#include "sdk.h"
#include <iostream>
#include <string>

Napi::String Method(const Napi::CallbackInfo &info)
{
    Napi::Env env = info.Env();
    char str[100];
    sdk::Test(str);
    return Napi::String::New(env, str);
}

Napi::Object Init(Napi::Env env, Napi::Object exports)
{
    exports.Set(Napi::String::New(env, "test"), Napi::Function::New(env, Method));
    return exports;
}

NODE_API_MODULE(sdkaddon, Init)
```

```json
-------------------------binding.gyp  重要 本地编译必要文件
{
  "targets": [
    {
      "target_name": "sdkaddon",
      'conditions': [
        [ 'OS=="win"', {
            "cflags!": [ "-fno-exceptions" ],
            "cflags_cc!": [ "-fno-exceptions" ],
            "sources": [ "sdkaddon.cc" ],
            "include_dirs": [
              "<!@(node -p \"require('node-addon-api').include\")",
              'sdk/include'
            ],
            'defines': [ 'NAPI_DISABLE_CPP_EXCEPTIONS' ],
            'link_settings': {
            'conditions': [
              ['target_arch=="ia32"', {
                'libraries': [
                  '<(PRODUCT_DIR)/../../sdk/lib/x86/sdk.lib',
                ],
                "copies": [
                  {
                    "destination": "build/Release",
                    "files": [
                      "sdk/lib/x86/sdk.dll"
                    ]
                  }
                ]
              },{
                'libraries': [
                  '<(PRODUCT_DIR)/../../sdk/lib/x64/sdk.lib',
                ],
                "copies": [
                  {
                    "destination": "build/Release",
                    "files": [
                      "sdk/lib/x64/sdk.dll"
                    ]
                  }
                ]
              }]
            ],
          },
        }]
      ],
    }
  ]
}
```

## 3. 编译执行

```shell
npm install
node-gyp rebuild
node .\index.js;
输出:hello world。
```

完成。
对于 js&c++大佬这个可能不是什么难事，但是我这个 c#程序员还是挺难的，折腾了老几天。。。记录一下希望帮助遇到和我同样问题的人。

全部源码：
https://github.com/DaZiYuan/nodejs-dynamiclink-example

