Update README.md

Author: heshanlk

README.md

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 # clean-code-javascript
 
 ## Table of Contents
-
-1. [Introduction](#introduction)
-2. [Variables](#variables)
-3. [Functions](#functions)
-4. [Objects and Data Structures](#objects-and-data-structures)
-5. [Classes](#classes)
-6. [SOLID](#solid)
-7. [Testing](#testing)
-8. [Concurrency](#concurrency)
-9. [Error Handling](#error-handling)
-10. [Formatting](#formatting)
-11. [Comments](#comments)
-12. [Translation](#translation)
+- [clean-code-javascript](#clean-code-javascript)
+  * [Table of Contents](#table-of-contents)
+  * [Introduction](#introduction)
+  * [**Variables**](#--variables--)
+    + [Use meaningful and pronounceable variable names](#use-meaningful-and-pronounceable-variable-names)
+    + [Use the same vocabulary for the same type of variable](#use-the-same-vocabulary-for-the-same-type-of-variable)
+    + [Use searchable names](#use-searchable-names)
+    + [Use explanatory variables](#use-explanatory-variables)
+    + [Avoid Mental Mapping](#avoid-mental-mapping)
+    + [Don't add unneeded context](#don-t-add-unneeded-context)
+    + [Use default arguments instead of short circuiting or conditionals](#use-default-arguments-instead-of-short-circuiting-or-conditionals)
+  * [**Functions**](#--functions--)
+    + [Function arguments (2 or fewer ideally)](#function-arguments--2-or-fewer-ideally-)
+    + [Functions should do one thing](#functions-should-do-one-thing)
+    + [Function names should say what they do](#function-names-should-say-what-they-do)
+    + [Functions should only be one level of abstraction](#functions-should-only-be-one-level-of-abstraction)
+    + [Remove duplicate code](#remove-duplicate-code)
+    + [Set default objects with Object.assign](#set-default-objects-with-objectassign)
+    + [Don't use flags as function parameters](#don-t-use-flags-as-function-parameters)
+    + [Avoid Side Effects (part 1)](#avoid-side-effects--part-1-)
+    + [Avoid Side Effects (part 2)](#avoid-side-effects--part-2-)
+    + [Don't write to global functions](#don-t-write-to-global-functions)
+    + [Favor functional programming over imperative programming](#favor-functional-programming-over-imperative-programming)
+    + [Encapsulate conditionals](#encapsulate-conditionals)
+    + [Avoid negative conditionals](#avoid-negative-conditionals)
+    + [Avoid conditionals](#avoid-conditionals)
+    + [Avoid type-checking (part 1)](#avoid-type-checking--part-1-)
+    + [Avoid type-checking (part 2)](#avoid-type-checking--part-2-)
+    + [Don't over-optimize](#don-t-over-optimize)
+    + [Remove dead code](#remove-dead-code)
+  * [**Objects and Data Structures**](#--objects-and-data-structures--)
+    + [Use getters and setters](#use-getters-and-setters)
+    + [Make objects have private members](#make-objects-have-private-members)
+  * [**Classes**](#--classes--)
+    + [Prefer ES2015/ES6 classes over ES5 plain functions](#prefer-es2015-es6-classes-over-es5-plain-functions)
+    + [Use method chaining](#use-method-chaining)
+    + [Prefer composition over inheritance](#prefer-composition-over-inheritance)
+  * [**SOLID**](#--solid--)
+    + [Single Responsibility Principle (SRP)](#single-responsibility-principle--srp-)
+    + [Open/Closed Principle (OCP)](#open-closed-principle--ocp-)
+    + [Liskov Substitution Principle (LSP)](#liskov-substitution-principle--lsp-)
+    + [Interface Segregation Principle (ISP)](#interface-segregation-principle--isp-)
+    + [Dependency Inversion Principle (DIP)](#dependency-inversion-principle--dip-)
+  * [**Testing**](#--testing--)
+    + [Single concept per test](#single-concept-per-test)
+  * [**Concurrency**](#--concurrency--)
+    + [Use Promises, not callbacks](#use-promises--not-callbacks)
+    + [Async/Await are even cleaner than Promises](#async-await-are-even-cleaner-than-promises)
+  * [**Error Handling**](#--error-handling--)
+    + [Don't ignore caught errors](#don-t-ignore-caught-errors)
+    + [Don't ignore rejected promises](#don-t-ignore-rejected-promises)
+  * [**Formatting**](#--formatting--)
+    + [Use consistent capitalization](#use-consistent-capitalization)
+    + [Function callers and callees should be close](#function-callers-and-callees-should-be-close)
+  * [**Comments**](#--comments--)
+    + [Only comment things that have business logic complexity.](#only-comment-things-that-have-business-logic-complexity)
+    + [Don't leave commented out code in your codebase](#don-t-leave-commented-out-code-in-your-codebase)
+    + [Don't have journal comments](#don-t-have-journal-comments)
+    + [Avoid positional markers](#avoid-positional-markers)
+  * [Translation](#translation)
 
 ## Introduction