Objects with Properties

Documentation

The global variablemyLib has a functionmakeGreeting for creating greetings,and a propertynumberOfGreetings indicating the number of greetings made so far.

Code

ts
letresult =myLib.makeGreeting("hello, world");
console.log("The computed greeting is:" +result);
letcount =myLib.numberOfGreetings;

Declaration

Usedeclare namespace to describe types or values accessed by dotted notation.

ts
declarenamespacemyLib {
functionmakeGreeting(s:string):string;
letnumberOfGreetings:number;
}

Overloaded Functions

Documentation

ThegetWidget function accepts a number and returns a Widget, or accepts a string and returns a Widget array.

Code

ts
letx:Widget =getWidget(43);
letarr:Widget[] =getWidget("all of them");

Declaration

ts
declarefunctiongetWidget(n:number):Widget;
declarefunctiongetWidget(s:string):Widget[];

Reusable Types (Interfaces)

Documentation

When specifying a greeting, you must pass aGreetingSettings object.This object has the following properties:

1 - greeting: Mandatory string

2 - duration: Optional length of time (in milliseconds)

3 - color: Optional string, e.g. ‘#ff00ff’

Code

ts
greet({
greeting:"hello world",
duration:4000
});

Declaration

Use aninterface to define a type with properties.

ts
interfaceGreetingSettings {
greeting:string;
duration?:number;
color?:string;
}
declarefunctiongreet(setting:GreetingSettings):void;

Reusable Types (Type Aliases)

Documentation

Anywhere a greeting is expected, you can provide astring, a function returning astring, or aGreeter instance.

Code

ts
functiongetGreeting() {
return"howdy";
}
classMyGreeterextendsGreeter {}
greet("hello");
greet(getGreeting);
greet(newMyGreeter());

Declaration

You can use a type alias to make a shorthand for a type:

ts
typeGreetingLike =string | (()=>string) |MyGreeter;
declarefunctiongreet(g:GreetingLike):void;

Organizing Types

Documentation

Thegreeter object can log to a file or display an alert.You can provide LogOptions to.log(...) and alert options to.alert(...)

Code

ts
constg =newGreeter("Hello");
g.log({verbose:true });
g.alert({modal:false,title:"Current Greeting" });

Declaration

Use namespaces to organize types.

ts
declarenamespaceGreetingLib {
interfaceLogOptions {
verbose?:boolean;
  }
interfaceAlertOptions {
modal:boolean;
title?:string;
color?:string;
  }
}

You can also create nested namespaces in one declaration:

ts
declarenamespaceGreetingLib.Options {
// Refer to via GreetingLib.Options.Log
interfaceLog {
verbose?:boolean;
  }
interfaceAlert {
modal:boolean;
title?:string;
color?:string;
  }
}

Classes

Documentation

You can create a greeter by instantiating theGreeter object, or create a customized greeter by extending from it.

Code

ts
constmyGreeter =newGreeter("hello, world");
myGreeter.greeting ="howdy";
myGreeter.showGreeting();
classSpecialGreeterextendsGreeter {
constructor() {
super("Very special greetings");
  }
}

Declaration

Usedeclare class to describe a class or class-like object.Classes can have properties and methods as well as a constructor.

ts
declareclassGreeter {
constructor(greeting:string);
greeting:string;
showGreeting():void;
}

Global Variables

Documentation

The global variablefoo contains the number of widgets present.

Code

ts
console.log("Half the number of widgets is " +foo /2);

Declaration

Usedeclare var to declare variables.If the variable is read-only, you can usedeclare const.You can also usedeclare let if the variable is block-scoped.

ts
/** The number of widgets present */
declarevarfoo:number;

Global Functions

Documentation

You can call the functiongreet with a string to show a greeting to the user.

Code

ts
greet("hello, world");

Declaration

Usedeclare function to declare functions.

ts
declarefunctiongreet(greeting:string):void;