Node.js | NPM 使用介绍

簡介

npm（全稱Node Package Manager，即「node包管理器」）是Node.js預設的、以JavaScript編寫的軟體套件管理系統。
它是一個線上套件庫，可以下載各式各樣的Javascript套件來使用。

使用場景

允許使用者從NPM伺服器下載別人編寫的第三方包到本機使用。
允許使用者從NPM伺服器下載並安裝別人編寫的指令行程序到本機使用。
允許使用者將自己編寫的包或指令行程序上傳到NPM伺服器供別人使用。

NPM 安裝

由於新版的Node.js已經集成了npm，所以之前npm也一併安裝好了。可以通過輸入

npm -v

來測試是否成功安裝。

如果你安裝的是舊版本的npm，可以很容易得通過npm指令來升級。

1	sudo npm install npm -g

NPM 指令介紹

安裝模組

npm安裝Node.js模組語法格式如下：

1	npm install <Module Name>

我們使用npm指令安裝常用的Node.js web框架模組express：

1	npm install express

安裝好之後，express包就放在了工程目錄下的node_modules目錄中

因此在程式中只需要通過require('express')的方式就好，無需指定第三方包路徑。

1	var express = require('express');

簡單的express範例：

var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send('Hello World!');
});

app.listen(3000, function () {
  console.log('Example app listening on port 3000!');
});

全域安裝、本機安装

npm的包安裝分為本機安裝(local)、全域安裝（global）兩種，從指令行來看，差別只是有沒有-g而已。

1 2	npm install express ## 本機安裝 npm install express -g ## 全域安裝

如果出現以下錯誤：

1	npm err! Error: connect ECONNREFUSED 127.0.0.1:8087

解決辦法為：

1	npm config set proxy null

本機安裝
- 將安裝包放在./node_modules下(運行npm指令時所在的目錄)，如果沒有node_modules目錄，會在當前執行npm指令的目錄下生成 node_modules目錄。
- 可以通過require()來引入本機安裝的包。
全局安裝
- 將安裝包放在/usr/local下或者你node的安裝目錄。
- 可以直接在指令行里使用。

查看安装訊息

1 2	npm list npm list -g ## 全域

如要查看某個模組版本號：

1	npm list express

package.json

package.json是存在於任何Node應用程序/模組的根目錄和用於定義一個包的屬性。

Package.json的屬性：

名稱	說明
name	包的名稱
version	包的版本
description	包的描述
homepage	包主頁
author	包的作者
contributors	貢獻者到包的名字
dependencies	依賴關係的列表。NPM自動安裝所有在這裡的包node_module文件夾中提到的依賴關係
repository	包的庫類型和URL
main	包的入口點
keywords	關鍵字

打開package.json在當前node_modules/express/

{
  "requires": true,
  "lockfileVersion": 1,
  "dependencies": {
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      "resolved": "https://registry.npmjs.org/accepts/-/accepts-1.3.7.tgz",
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      "requires": {
        "mime-types": "~2.1.24",
        "negotiator": "0.6.2"
      }
    },
    "array-flatten": {
      "version": "1.1.1",
      "resolved": "https://registry.npmjs.org/array-flatten/-/array-flatten-1.1.1.tgz",
      "integrity": "sha1-ml9pkFGx5wczKPKgCJaLZOopVdI="
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      "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-1.19.0.tgz",
      "integrity": "sha512-dhEPs72UPbDnAQJ9ZKMNTP6ptJaionhP5cBb541nXPlW60Jepo9RV/a4fX4XWW9CuFNK22krhrj1+rgzifNCsw==",
      "requires": {
        "bytes": "3.1.0",
        "content-type": "~1.0.4",
        "debug": "2.6.9",
        "depd": "~1.1.2",
        "http-errors": "1.7.2",
        "iconv-lite": "0.4.24",
        "on-finished": "~2.3.0",
        "qs": "6.7.0",
        "raw-body": "2.4.0",
        "type-is": "~1.6.17"
      }
    },
    "bytes": {
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      "resolved": "https://registry.npmjs.org/bytes/-/bytes-3.1.0.tgz",
      "integrity": "sha512-zauLjrfCG+xvoyaqLoV8bLVXXNGC4JqlxFCutSDWA6fJrTo2ZuvLYTqZ7aHBLZSMOopbzwv8f+wZcVzfVTI2Dg=="
    },
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      "resolved": "https://registry.npmjs.org/content-disposition/-/content-disposition-0.5.3.tgz",
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      "resolved": "https://registry.npmjs.org/content-type/-/content-type-1.0.4.tgz",
      "integrity": "sha512-hIP3EEPs8tB9AT1L+NUqtwOAps4mk2Zob89MWXMHjHWg9milF/j4osnnQLXBCBFBk/tvIG/tUc9mOUJiPBhPXA=="
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      "resolved": "https://registry.npmjs.org/cookie/-/cookie-0.4.0.tgz",
      "integrity": "sha512-+Hp8fLp57wnUSt0tY0tHEXh4voZRDnoIrZPqlo3DPiI4y9lwg/jqx+1Om94/W6ZaPDOUbnjOt/99w66zk+l1Xg=="
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    "cookie-signature": {
      "version": "1.0.6",
      "resolved": "https://registry.npmjs.org/cookie-signature/-/cookie-signature-1.0.6.tgz",
      "integrity": "sha1-4wOogrNCzD7oylE6eZmXNNqzriw="
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      "resolved": "https://registry.npmjs.org/debug/-/debug-2.6.9.tgz",
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      "integrity": "sha1-m81S4UwJd2PnSbJ0xDRu0uVgtak="
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    "destroy": {
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      "integrity": "sha1-l4hXRCxEdJ5CBmE+N5RiBYJqvYA="
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      "resolved": "https://registry.npmjs.org/ee-first/-/ee-first-1.1.1.tgz",
      "integrity": "sha1-WQxhFWsK4vTwJVcyoViyZrxWsh0="
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      "requires": {
        "accepts": "~1.3.7",
        "array-flatten": "1.1.1",
        "body-parser": "1.19.0",
        "content-disposition": "0.5.3",
        "content-type": "~1.0.4",
        "cookie": "0.4.0",
        "cookie-signature": "1.0.6",
        "debug": "2.6.9",
        "depd": "~1.1.2",
        "encodeurl": "~1.0.2",
        "escape-html": "~1.0.3",
        "etag": "~1.8.1",
        "finalhandler": "~1.1.2",
        "fresh": "0.5.2",
        "merge-descriptors": "1.0.1",
        "methods": "~1.1.2",
        "on-finished": "~2.3.0",
        "parseurl": "~1.3.3",
        "path-to-regexp": "0.1.7",
        "proxy-addr": "~2.0.5",
        "qs": "6.7.0",
        "range-parser": "~1.2.1",
        "safe-buffer": "5.1.2",
        "send": "0.17.1",
        "serve-static": "1.14.1",
        "setprototypeof": "1.1.1",
        "statuses": "~1.5.0",
        "type-is": "~1.6.18",
        "utils-merge": "1.0.1",
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        "on-finished": "~2.3.0",
        "parseurl": "~1.3.3",
        "statuses": "~1.5.0",
        "unpipe": "~1.0.0"
      }
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      "integrity": "sha1-mMI9qxF1ZXuMBXPozszZGw/xjIQ="
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      "resolved": "https://registry.npmjs.org/fresh/-/fresh-0.5.2.tgz",
      "integrity": "sha1-PYyt2Q2XZWn6g1qx+OSyOhBWBac="
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    "http-errors": {
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      "resolved": "https://registry.npmjs.org/http-errors/-/http-errors-1.7.2.tgz",
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    "utils-merge": {
      "version": "1.0.1",
      "resolved": "https://registry.npmjs.org/utils-merge/-/utils-merge-1.0.1.tgz",
      "integrity": "sha1-n5VxD1CiZ5R7LMwSR0HBAoQn5xM="
    },
    "vary": {
      "version": "1.1.2",
      "resolved": "https://registry.npmjs.org/vary/-/vary-1.1.2.tgz",
      "integrity": "sha1-IpnwLG3tMNSllhsLn3RSShj2NPw="
    }
  }
}

卸载模組

1	npm uninstall express

更新模組

1	npm update express

搜尋模組

1	npm search express

總結

這篇文章僅僅介紹簡單常用的一些指令，還有一些指令沒有特別列出來，是因為將來才會特別用一篇文章來做介紹，像「建立模組」、「發布模組」之類的，這些到後面再來做介紹也不遲。

錯誤處理

no such file or directory, open ‘/package.json’

$ npm install express --save
npm WARN saveError ENOENT: no such file or directory, open '/Users/morose/Documents/Temp/Example/package.json'
npm WARN enoent ENOENT: no such file or directory, open '/Users/morose/Documents/Temp/Example/package.json'
npm WARN Example No description
npm WARN Example No repository field.
npm WARN Example No README data
npm WARN Example No license field.

+ express@4.17.1
removed 1 package, updated 1 package and audited 764 packages in 2.289s

2 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities



   ╭────────────────────────────────────────────────────────────────╮
   │                                                                │
   │      New patch version of npm available! 6.13.6 → 6.13.7       │
   │   Changelog: https://github.com/npm/cli/releases/tag/v6.13.7   │
   │               Run npm install -g npm to update!                │
   │                                                                │
   ╰────────────────────────────────────────────────────────────────╯

原因：因為缺少package.json所以無法install。

解決：將其初始化

1	npm init -f

註：-f表示force的意思，不加這個，npm會讓你輸入一堆訊息，比如name、version之類，如果只是做做實驗小demo，直接-f，npm幫你初始化package.json，並填充各種默認值，省事。

npm ERR! also called “”. Did you name your project the same

$ npm install express --save
npm ERR! code ENOSELF
npm ERR! Refusing to install package with name "express" under a package
npm ERR! also called "express". Did you name your project the same
npm ERR! as the dependency you're installing?
npm ERR!
npm ERR! For more information, see:
npm ERR!     <https://docs.npmjs.com/cli/install#limitations-of-npms-install-algorithm>

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/morose/.npm/_logs/2020-02-06T02_44_10_640Z-debug.log

原因：安裝目錄的名稱與要安裝的模組名稱相同造成。

解決：將目錄名稱修改成非模組名稱，然後安裝。

1	npm install express --save

註：--save表示將安裝的包加入依賴列表的意思，可以看下package.json裡的dependencies字段。後面再運行npm install，就會把所有依賴安裝下來。如果不加--save，什麼都不會安裝。

註：以上參考了
從零開始: 使用NPM套件
 NPM 使用介绍
 express Hello world 範例

Node.js | 第一個 Hello World

Node.js | REPL終端

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