Install nodejs or nvm
For Windows: Node Version Manager (nvm) for Windows
IDE Visual Studio Code:
https://code.visualstudio.com/docs?dv=win
TypeScript Playground
https://www.typescriptlang.org/play?#
Install typescript
npm install -g typescript
Result:
C:\Users\Administrator>npm install -g typescript C:\Program Files\nodejs\tsserver -> C:\Program Files\nodejs\node_modules\typescr ipt\bin\tsserver C:\Program Files\nodejs\tsc -> C:\Program Files\nodejs\node_modules\typescript\b in\tsc C:\Program Files\nodejs `-- typescript@3.9.7
Verify:
C:\Users\Administrator>tsc --version Version 3.9.7
Compile typescript
tsc file1.ts, file2.ts, file3.ts
Identifiers in TypeScript
- Identifiers can include both, characters and digits. However, the identifier cannot begin with a digit.
- Identifiers cannot include special symbols except for underscore (_) or a dollar sign ($).
- Identifiers cannot be keywords.
- They must be unique.
- Identifiers are case-sensitive.
- Identifiers cannot contain spaces.
TypeScript ─ Keywords
Keywords have a special meaning in the context of a language. The following table lists some keywords in TypeScript.
| break | as | any | switch |
| case | if | throw | else |
| var | number | string | get |
| module | type | instanceof | typeof |
| public | private | enum | export |
| finally | for | while | void |
| null | super | this | new |
| in | return | true | false |
| any | extends | static | let |
| package | implements | interface | function |
| new | try | yield | const |
| continue | do | catch | yeild |
| async | await | of | self |
Comments in TypeScript
- Single-line comments ( // )
- Multi-line comments (/* */)
TypeScript and Object Orientation
- Object − An object is a real time representation of any entity. According to Grady Brooch, every object must have three features −
- State − described by the attributes of an object
- Behavior − describes how the object will act
- Identity − a unique value that distinguishes an object from a set of similar such objects.
- Class − A class in terms of OOP is a blueprint for creating objects. A class encapsulates data for the object.
- Method − Methods facilitate communication between objects.
Example:
class Animal {
say():void {
console.log("Hello World!!!")
}
}
var obj = new Animal();
obj.say();
After compiling
var Animal = /** @class */ (function () {
function Animal() {
}
Animal.prototype.say = function () {
console.log("Hello World!!!");
};
return Animal;
}());
var obj = new Animal();
obj.say();
TypeScript – Types
The Any type
The any data type is the super type of all types in TypeScript. It denotes a dynamic type. Using the any type is equivalent to opting out of type checking for a variable.
Built-in types
| Data type | Keyword | Description |
|---|---|---|
| Number | number | Double precision 64-bit floating point values. It can be used to represent both, integers and fractions. |
| String | string | Represents a sequence of Unicode characters |
| Boolean | boolean | Represents logical values, true and false |
| Void | void | Used on function return types to represent non-returning functions |
| Null | null | Represents an intentional absence of an object value. |
| Undefined | undefined | Denotes value given to all uninitialized variables |
| Symbol | symbol | |
| Unknown | unknown | We may need to describe the type of variables that we do not know when we are writing an application. These values may come from dynamic content
Example let notSure: unknown = 4 notSure = "maybe a string instead" // OK, definitely a boolean notSure = false |
| Never | never | represents the type of values that never occur.
Example function error(message: string): never {
throw new Error(message)
}
|
| Object | object | is a type that represents the non-primitive type, i.e. anything that is not number, string, boolean, symbol, null, or undefined.
Example var str = typeof(Object.create({}))
console.log(str) //object
|
User-defined Types
User-defined types include Enumerations (enums), classes, interfaces, arrays, and tuple.
