[Feature] 30-days-of-javaScript

public/30-days-of-javaScript.md

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+---
+title: 30-days-of-javaScript
+tags:
+  - 'javascript'
+private: false
+updated_at: ''
+id: null
+organization_url_name: null
+slide: false
+ignorePublish: false
+---
+
+# 概要
+
+[30 Days of JavaScript](https://leetcode.com/studyplan/30-days-of-javascript/) でJavaScriptの基礎を学ぶためのプランをやってみる。
+
+# 進捗
+
+## 2667. Create Hello World Function
+
+> Write a function createHelloWorld. It should return a new function that always returns "Hello World".
+
+```javascript
+function createHelloWorld() {
+  return function (...args) {
+    return "Hello World";
+  };
+}
+
+// Example 1
+const f1 = createHelloWorld();
+console.log(f1()); // Output: "Hello World"
+
+// Example 2
+const f2 = createHelloWorld();
+console.log(f2({}, null, 42)); // Output: "Hello World"
+```
+
+## 2620. Counter
+
+> Given an integer n, return a counter function. This counter function initially returns n and then returns 1 more than
+> the previous value every subsequent time it is called (n, n + 1, n + 2, etc).
+
+```javascript
+/**
+ * @param {number} n
+ * @return {Function} counter
+ */
+var createCounter = function (n) {
+  return function () {
+    return n++;
+  };
+};
+
+/**
+ * const counter = createCounter(10)
+ * counter() // 10
+ * counter() // 11
+ * counter() // 12
+ */
+```
+
+##
+
+```javascript
+/**
+ * @param {string} val
+ * @return {Object}
+ */
+var expect = function (val) {
+  return {
+    /**
+     * toBe(val) accepts another value and returns true
+     * if the two values === each other. If they are not equal,
+     * it should throw an error "Not Equal".
+     * @param expected
+     */
+    toBe: function (expected) {
+      if (val !== expected) {
+        throw new Error("Not Equal");
+      }
+
+      return true;
+    },
+    /**
+     * notToBe(val) accepts another value and returns true
+     * if the two values !== each other. If they are equal,
+     * it should throw an error "Equal".
+     */
+    notToBe: function (expected) {
+      if (val === expected) {
+        throw new Error("Equal");
+      }
+
+      return true;
+    },
+  };
+};
+/**
+ * expect(5).toBe(5); // true
+ * expect(5).notToBe(5); // throws "Equal"
+ */
+```
+
+## 2704. To Be Or Not To Be
+
+> Write a function expect that helps developers test their code. It should take in any value val and return an object
+> with the following two functions.
+>
+> toBe(val) accepts another value and returns true if the two values === each other. If they are not equal, it should
+> throw an error "Not Equal".
+> notToBe(val) accepts another value and returns true if the two values !== each other. If they are equal, it should
+> throw an error "Equal".
+
+```javascript
+/**
+ * @param {string} val
+ * @return {Object}
+ */
+var expect = function (val) {
+  return {
+    /**
+     * toBe(val) accepts another value and returns true
+     * if the two values === each other. If they are not equal,
+     * it should throw an error "Not Equal".
+     * @param expected
+     */
+    toBe: function (expected) {
+      if (val !== expected) {
+        throw new Error("Not Equal");
+      }
+
+      return true;
+    },
+    /**
+     * notToBe(val) accepts another value and returns true
+     * if the two values !== each other. If they are equal,
+     * it should throw an error "Equal".
+     */
+    notToBe: function (expected) {
+      if (val === expected) {
+        throw new Error("Equal");
+      }
+
+      return true;
+    },
+  };
+};
+/**
+ * expect(5).toBe(5); // true
+ * expect(5).notToBe(5); // throws "Equal"
+ */
+```