first functions

Author: than-dev

.gitignore

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+node_modules/
+yarn.lock

@types/at.d.ts

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+/**
+ * @param {number} index
+ */
+export function at(index: number): any;

@types/foreach.d.ts

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+/**
+ * @param {Function} callback
+ * @param {any | undefined} thisArg
+ */
+export function forEach(callback: Function, thisArg?: any | undefined): void;

@types/map.d.ts

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+/**
+ * @param {Function} callback
+ * @param {any | undefined} thisArg
+ */
+export function map(callback: Function, thisArg?: any | undefined): any[];

@types/reduce.d.ts

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+/**
+ * @param {Function} callback
+ * @param {any | undefined} initialValue
+ */
+export function reduce(callback: Function, initialValue?: any | undefined): any;

functions/at.js

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+Array.prototype.at = at
+
+
+/**
+ * @param {number} index
+ */
+function at(index) {
+    if (typeof index !== 'number') {
+        throw new Error(`param need to be a number but receive a ${typeof index }`)
+    }
+    
+    const array = this
+    
+    if (index > 0) {
+        return array[index]
+    } else {
+        let handleArrayPosition = 0;
+        
+        for (let i = array.length - 1; i > -1; i--) {
+            handleArrayPosition--
+
+            if (handleArrayPosition == index) {
+                return array[i]
+            }
+        }
+    }
+}
+
+module.exports = { at }

functions/foreach.js

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+Array.prototype.forEach = forEach
+
+/**
+ * @param {Function} callback
+ * @param {any | undefined} thisArg
+ */
+function forEach(callback, thisArg = undefined) {
+	if (typeof callback !== 'function') {
+		throw new Error(`Second param must be a function but received ${typeof callback}`)
+	}
+	
+	const array = this
+
+	for (let i = 0; i < array.length; i++) {
+		callback.apply(thisArg, [array[i], i, array])
+	}
+}
+
+module.exports = { forEach }

functions/map.js

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+Array.prototype.map = map
+
+/**
+ * @param {Function} callback
+ * @param {any | undefined} thisArg
+ */
+function map(callback, thisArg = undefined) {
+	if (typeof callback !== 'function') {
+		throw new Error(`Second param must be a function but received ${typeof callback}`)
+	}
+
+	const array = this
+	let newArray = []
+
+	for (let i = 0; i < array.length; i++) {
+		const newElement = callback.apply(thisArg, [array[i], i, array])
+
+		newArray.push(newElement)
+	}
+
+	return newArray
+}
+
+
+
+['oi', 'oi', 'oi'].map((element, elementPosition, array) => console.log({
+	element,
+	elementPosition,
+	array
+}))
+
+module.exports = { map }

functions/reduce.js

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+Array.prototype.reduce = reduce
+
+/**
+ * @param {Function} callback
+ * @param {any | undefined} initialValue
+ */
+function reduce(callback, initialValue = undefined) {
+    if (typeof callback !== 'function') {
+		throw new Error(`Second param must be a function but received ${typeof callback}`)
+	}
+	
+    const array = this
+    let accumulator = initialValue ? initialValue : array[0] 
+
+	for (let i = 0; i < array.length; i++) {
+		const newAcc = callback(accumulator, array[i], i, array)
+
+        accumulator = newAcc
+    }
+    
+    return accumulator
+}
+
+
+module.exports = { reduce }

package.json

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+{
+  "name": "JS-Functions",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "typings": "./@types/map.d.ts",
+  "scripts": {
+    "compile-declarations": "tsc --declaration",
+    "clean-declarations": "tsc --declaration --clean"
+  },
+  "devDependencies": {
+    "@types/node": "^16.4.4",
+    "typescript": "^4.3.5"
+  },
+  "dependencies": {
+    "tsd": "^0.17.0"
+  }
+}