From 54c0dcd30577fa9da865ec441986d99f3f294176 Mon Sep 17 00:00:00 2001
From: Shantanu Dutta <7542135+nlern@users.noreply.github.com>
Date: Mon, 9 Sep 2019 07:44:19 +0530
Subject: [PATCH] 1. Added npm start script. 2. Simplified logic for binary to
 decimal conversion.

---
 .../1. Bin2Dec/Web/index.js                   | 82 ++++++++-----------
 .../1. Bin2Dec/Web/package.json               |  1 +
 2 files changed, 35 insertions(+), 48 deletions(-)

diff --git a/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/index.js b/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/index.js
index 03478a90..1632357f 100644
--- a/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/index.js	
+++ b/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/index.js	
@@ -1,74 +1,60 @@
-(function (document, window, domIsReady, undefined) {
-
-  function convertBin2Dec(binaryExpr) {
-    const bin2Dec = {
-      '0000': 0,
-      '0001': 1,
-      '0010': 2,
-      '0011': 3,
-      '0100': 4,
-      '0101': 5,
-      '0110': 6,
-      '0111': 7,
-      '1000': 8,
-      '1001': 9,
-      '1010': 10,
-      '1011': 11,
-      '1100': 12,
-      '1101': 13,
-      '1110': 14,
-      '1111': 15,
-    };
-    const len = binaryExpr.length;
-    binaryExpr = len % 4 === 0 ? binaryExpr : '0'.repeat(4 - len % 4) + binaryExpr;
-    
-    const maxPow = binaryExpr.length / 4;
-    let result = 0, pow = 1;
-    for (let i = 0; i < maxPow; i++) {
-      result += bin2Dec[binaryExpr.slice(4 * i, 4 * (i + 1))] * pow;
-      pow *= 16;
-    }
+((document, window, domIsReady, undefined) => {
+  const convertBin2Dec = binaryExpr => {
+    // Formulae
+    // input = 1 => output = 1*(2^0) = 1
+    // input = 10 => Output = (0*(2^0))+(1*(2^1)) = 2
+    // so we reverse and iterate from the back
+    const reverseBinaryText = binaryExpr
+      .split("")
+      .map(Number) // convert to number from string
+      .reverse();
+    // claculate the result by accumulating previous value
+    const result = reverseBinaryText.reduce(
+      (accumulator, currentValue, indx) =>
+        accumulator + currentValue * Math.pow(2, indx)
+    );
 
     return result;
-  }
+  };
 
-  function validate() {
-    const formEl = document.getElementById('form');
-    const inputEl = formEl.querySelector('input');
-    const errMsgEl = formEl.querySelector('.error-message');
-    const outEl = document.getElementById('output');
+  const validate = () => {
+    const formEl = document.getElementById("form");
+    const inputEl = formEl.querySelector("input");
+    const errMsgEl = formEl.querySelector(".error-message");
+    const outEl = document.getElementById("output");
 
-    let expr = '', isValid = false;
+    let expr = "",
+      isValid = false;
 
     const handleValid = () => {
-      errMsgEl.className = 'error-message hidden';
-      errMsgEl.innerHTML = '';
+      errMsgEl.className = "error-message hidden";
+      errMsgEl.innerHTML = "";
       const decExpr = convertBin2Dec(expr);
       outEl.innerHTML = `Decimal equivalent of ${expr} : ${decExpr}`;
     };
 
     const handleInvalid = () => {
-      errMsgEl.className = 'error-message';
+      errMsgEl.className = "error-message";
       if (expr.length === 0) {
-        errMsgEl.innerHTML = 'Please enter a binary expression';
+        errMsgEl.innerHTML = "Please enter a binary expression";
       }
       if (/[^0-1]+/g.test(expr)) {
-        errMsgEl.innerHTML = 'Only 0, 1 is allowed!';
+        errMsgEl.innerHTML = "Only 0, 1 is allowed!";
         return;
       }
     };
 
-    formEl.addEventListener('submit', e => e.preventDefault());
+    formEl.addEventListener("submit", e => e.preventDefault());
 
-    inputEl.addEventListener('keyup', (e) => {
-      outEl.innerHTML = '';
+    inputEl.addEventListener("keyup", e => {
+      outEl.innerHTML = "";
       expr = e.target.value;
       const validInputRegEx = /^[0-1]+$/g;
       isValid = validInputRegEx.test(expr);
       isValid ? handleValid() : handleInvalid();
     });
-  }
-  domIsReady(function () {
+  };
+  domIsReady(() => {
     validate();
   });
-})(document, window, domIsReady);
\ No newline at end of file
+})(document, window, domIsReady);
diff --git a/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/package.json b/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/package.json
index 64ad6111..54fabb8f 100644
--- a/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/package.json	
+++ b/Solutions/1. Tier 1 - Begineer Projects/1. Bin2Dec/Web/package.json	
@@ -4,6 +4,7 @@
   "description": "",
   "main": "index.js",
   "scripts": {
+    "start": "lite-server",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "keywords": [],