Learn Basic Concept in TypeScript Day -9

 In this article ..we are learn basic concept in TypeScript.

Variable Declaration:

Variable: Variable is a named place in memory where some data/value can be stored. According to the word variable, it can be said that the value of a variable can be changed/vary. 

While declaring a variable  some rules have to be followed:

1. Variable  name can contains alphabets both Upper-case as well as Lower-case and digits also.

2.Variable name cant start with digit.

3.We can use _ and $ special character only, apart from these other special characters are not allowed.

Variable declaration: 

A variable must be declared before it is used.use the bar keyword to declare a variable.

We  can declare a  variable in  multiple ways like below:

var Identifier:Data-type = value;

var Identifier: Data-type;

var Identifier = value;

var Identifier;

Examples:

1.var name:number = 10; Here name is a variable which can store only Integer type data.

2.var name:number; Here name is a variable which can store only Integer type data. But by

default its value set to undefined.

3.var name = 10; Here while declaring variable we are not specifying data-type. Therefore

compiler decide its data type by seeing its value i.e. number here.

4.var name; Here while declaring variable we are not specifying data-type as well as we are not 

assigning any value also. then compiler takes its data type as any.its value is set to undefined by default.

Creating object:

• An object is an instance of class which contains set of key value pairs.
•  It’s value may be scalar values or functions or even array of other objects.

  

Syntax of creating a object:

var object_name = new class_name();

Creating class:

• Class 
  term of OOPs is a blueprint for creating objects.
• In class group of objects which have common properties. 
• Class contain fields, methods,  constructors, Blocks, Nested class and interface.
• Use the class keyword to declare a class in TypeScript.

Syntax to declare a class:

class class_Name{    

    field;    

    method;    

}

Import:

• Importing is just about as easy as exporting from a module. 
• A statement to use primitive values, objects, functions, or classes that are exported from another module. Typically, an import is static, but it can be dynamic too
• Importing an exported declaration is done through using one of the import forms below:
• Import a single export from a module

import { ZipCodeValidator } from "./ZipCodeValidator";

let myValidator = new ZipCodeValidator();

Example:

Export:

• A statement to export primitive values, objects, functions, or classes from the module for the purpose of being used by other modules.
• Exporting a declaration Any declaration (such as a variable, function, class, type alias, or interface) can be exported by adding the export keyword.
  
  
  StringValidator.ts
  export interface StringValidator {
    isAcceptable(s: string): boolean;
  }

Example:

TypeScript Configuration:

• The tsconfig.json file indicates the root directory of TypeScript.
• The tsconfig.json file specifies the root files as well as the compiler options for compiling a program.
• As we run tsc command for each .ts file for converting it into .js file. The tsconfig.json file converts the all .ts file into .js and make our work easy.
• For tsconfig.json file run following command on terminal :

                             > tsc --init

• The above command automatically creates a tsconfig.json file.

• We can use a "outDir" for creating a new folder which having the .js files of our module, as i created in above image.

Thank you...