既存パッケージの利用とパッケージの作成

app.js

@@ -1 +1,6 @@
 'use strict';
+const axios = require('axios');
+//then->処理が完了(axios.get)したら次の処理を行わせる
+axios.get('http://www.google.com').then(res => {
+    console.log(res.data);
+});

package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "axios": "^1.3.3"
+  }
+}

sum-app/app.js

@@ -0,0 +1,3 @@
+'use strict';
+const s = require('sum');
+console.log(s.add([1, 2, 3, 4]));

sum-app/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "sum-app",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "dependencies": {
+    "sum": "../sum"
+  }
+}

sum-app/yarn.lock

@@ -0,0 +1,6 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+sum@../sum:
+  version "1.0.0"

sum/index.js

@@ -0,0 +1,20 @@
+'use strict';
+
+/**
+ * 数値の配列を受け取って、その要素の合計を返す関数
+ */
+function add(numbers) {
+    let result = 0;
+    for(const num of numbers) {
+        result = result + num;
+    }
+    return result;
+}
+
+//モジュールとして他のファイルから使えるようにする時
+//①module.exportsにオブジェクトとして代入する
+//②プロパティは外から見える名前,値は中身(関数)
+//③プロパティと値の名前が一致するときはプロパティ名を省略した方が良い
+module.exports = {
+    add
+};

sum/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "sum",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT"
+}

yarn.lock

@@ -0,0 +1,60 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+asynckit@^0.4.0:
+  version "0.4.0"
+  resolved "https://registry.yarnpkg.com/asynckit/-/asynckit-0.4.0.tgz#c79ed97f7f34cb8f2ba1bc9790bcc366474b4b79"
+  integrity sha512-Oei9OH4tRh0YqU3GxhX79dM/mwVgvbZJaSNaRk+bshkj0S5cfHcgYakreBjrHwatXKbz+IoIdYLxrKim2MjW0Q==
+
+axios@^1.3.3:
+  version "1.3.3"
+  resolved "https://registry.yarnpkg.com/axios/-/axios-1.3.3.tgz#e7011384ba839b885007c9c9fae1ff23dceb295b"
+  integrity sha512-eYq77dYIFS77AQlhzEL937yUBSepBfPIe8FcgEDN35vMNZKMrs81pgnyrQpwfy4NF4b4XWX1Zgx7yX+25w8QJA==
+  dependencies:
+    follow-redirects "^1.15.0"
+    form-data "^4.0.0"
+    proxy-from-env "^1.1.0"
+
+combined-stream@^1.0.8:
+  version "1.0.8"
+  resolved "https://registry.yarnpkg.com/combined-stream/-/combined-stream-1.0.8.tgz#c3d45a8b34fd730631a110a8a2520682b31d5a7f"
+  integrity sha512-FQN4MRfuJeHf7cBbBMJFXhKSDq+2kAArBlmRBvcvFE5BB1HZKXtSFASDhdlz9zOYwxh8lDdnvmMOe/+5cdoEdg==
+  dependencies:
+    delayed-stream "~1.0.0"
+
+delayed-stream@~1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/delayed-stream/-/delayed-stream-1.0.0.tgz#df3ae199acadfb7d440aaae0b29e2272b24ec619"
+  integrity sha512-ZySD7Nf91aLB0RxL4KGrKHBXl7Eds1DAmEdcoVawXnLD7SDhpNgtuII2aAkg7a7QS41jxPSZ17p4VdGnMHk3MQ==
+
+follow-redirects@^1.15.0:
+  version "1.15.2"
+  resolved "https://registry.yarnpkg.com/follow-redirects/-/follow-redirects-1.15.2.tgz#b460864144ba63f2681096f274c4e57026da2c13"
+  integrity sha512-VQLG33o04KaQ8uYi2tVNbdrWp1QWxNNea+nmIB4EVM28v0hmP17z7aG1+wAkNzVq4KeXTq3221ye5qTJP91JwA==
+
+form-data@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/form-data/-/form-data-4.0.0.tgz#93919daeaf361ee529584b9b31664dc12c9fa452"
+  integrity sha512-ETEklSGi5t0QMZuiXoA/Q6vcnxcLQP5vdugSpuAyi6SVGi2clPPp+xgEhuMaHC+zGgn31Kd235W35f7Hykkaww==
+  dependencies:
+    asynckit "^0.4.0"
+    combined-stream "^1.0.8"
+    mime-types "^2.1.12"
+
+mime-db@1.52.0:
+  version "1.52.0"
+  resolved "https://registry.yarnpkg.com/mime-db/-/mime-db-1.52.0.tgz#bbabcdc02859f4987301c856e3387ce5ec43bf70"
+  integrity sha512-sPU4uV7dYlvtWJxwwxHD0PuihVNiE7TyAbQ5SWxDCB9mUYvOgroQOwYQQOKPJ8CIbE+1ETVlOoK1UC2nU3gYvg==
+
+mime-types@^2.1.12:
+  version "2.1.35"
+  resolved "https://registry.yarnpkg.com/mime-types/-/mime-types-2.1.35.tgz#381a871b62a734450660ae3deee44813f70d959a"
+  integrity sha512-ZDY+bPm5zTTF+YpCrAU9nK0UgICYPT0QtT1NZWFv4s++TNkcgVaT0g6+4R2uI4MjQjzysHB1zxuWL50hzaeXiw==
+  dependencies:
+    mime-db "1.52.0"
+
+proxy-from-env@^1.1.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/proxy-from-env/-/proxy-from-env-1.1.0.tgz#e102f16ca355424865755d2c9e8ea4f24d58c3e2"
+  integrity sha512-D+zkORCbA9f1tdWRK0RaCR3GPv50cMxcrz4X8k5LTSUD1Dkw47mKJEZQNunItRTkWwgtaUSo1RVFRIG9ZXiFYg==