Code challange 4

.eslintrc.json

@@ -0,0 +1,27 @@
+{
+    "env": {
+      "browser": true,
+      "node": true,
+      "commonjs": true,
+      "jest": true,
+      "es6": true
+    },
+    "globals": {
+      "err": true,
+      "req": true,
+      "res": true,
+      "next": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+      "sourceType": "module"
+    },
+    "rules": {
+      "no-console": "off",
+      "indent": [ "error", 2 ],
+      "quotes": ["error", "single", { "allowTemplateLiterals": true }],
+      "comma-dangle": ["error", "always-multiline"],
+      "semi": [ "error", "always" ]
+    }
+  }
+

README.md

@@ -1,6 +1,13 @@
-# Table of Contents
-[1- code challange class 2 array shift ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/3)
+## Challenge Description
 
-[2- code challange class 3 array binary search ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/2)
+ to write a function to accepts an integer, and returns the nth number in the Fibonacci sequence.
 
-[
+## Approach & Efficiency
+
+i use Fibonacci Sequence approch , which is a set of numbers :
+ 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 
+next number is found by adding up the two numbers before it.
+
+## Solution
+
+![UML](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/blob/code-challange-4/20200203_213419.jpg)

challanges/code-challange-4/code-challange-4.js

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+'use strict';
+function fibFunction(x){
+  let array = [0, 1];
+  for (let i = array.length; i < x + 1; i++){
+    let sum = array[i - 2] + array[i -1];
+    array.push(sum);
+  }
+  return array[x];
+}
+
+module.exports = fibFunction ;

challanges/code-challange-4/code-challange-4.test.js

@@ -0,0 +1,7 @@
+'use strict';
+let validator = require('./code-challange-4.js');
+describe('Fibonacci Module',()=>{
+  it('validate  the output arr  ' ,()=> {
+    expect(validator(8)).toEqual( 21 );
+  });
+});