Addition of typescirpt syling guidelines

languages/typescript.md

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+# Typescript Styling Guidelines
+
+Guidelines for Typescript language
+
+## Names
+1. Use PascalCase for type names.
+2. Do not use "I" as a prefix for interface names.
+3. Use PascalCase for enum values.
+4. Use camelCase for function names.
+5. Function names should start with a verb (get, set, update, put, send, is...)
+6. Use camelCase for property names and local variables.
+7. Do not use "_" as a prefix for private properties.
+8. Use whole words in names when possible.
+9. Single letter variables are discouraged except for cases where definition can be inferred (e.g. i = index).
+
+## null and undefined
+1. use undefined, do not use null.
+
+## Flags
+1. More than 2 related boolean properties on a type shoudl be turned into a flag.
+
+## Comments
+1. Use of [JSDoc](https://github.com/shri/JSDoc-Style-Guide) style comments for functions, interfaces, enums and classes is encouraged.
+2. In line comments shall be used sparingly, code should be easily readable and logic flow should be apparent.
+
+## Strings
+1. Use Single quotes for strings.
+2. Prefer template strings over concat strings eg ``My name is ${name}`` vs `'My Name is ' + name`
+
+## Diagnostic and Error Messages
+1. Use a period at the end of a sentence.
+2. Use indfinite articles for indefinite entities.
+3. Definite entities should be named ("User was not updated", "Role could not be applied to User").
+4. When stating a rule, the subject should be in the singular ("A password cannot be shorter than 3 characters" instead of "Passwords cannot be ...")
+5. Use present tense.
+
+## General Constructs
+1. Do not use for..in statements; instead use `ts.forEach`.
+2. Try to use `ts.forEach`, `ts.map`, and `ts.filter` instead of loops when it is not strongly inconvenient.
+
+## Style
+1. Use arrow functions over anonymous function expressions.
+2. Only surround arrow functions parameters when necessary.
+3. Always surround loop and conditional bodies with curly braces (tsLint forces this by default as well).
+4. Open curly braces always go on the same line as whatever necessitates them.
+5. Parenthesized constructs should have no surrounding whitespace.
+6. Use a single declaration per variable statement (`var x = 1; var y = 3;` over `var x = 1, y = 2`).
+7. Else goes on the same line as the closing curly brace.
+8. Four(4) spaces per indentation.
+9. Classes end with new line character.
+10. Ternary operators never fail or succeed to another ternary eg `true ? '1' : true2 ? '2' : ''`
+11. If you need to drop to a new line, operators will stay on previous line eg 
+
+        ```
+            this.isTrue(true) ?
+                true :
+                false
+
+            return this && this.isTrue() &&
+                !this.isFalse()
+        ```