Constructor in TypeScript
Constructors are identified with keyword "constructor". A Constructor is a special type of method of a class and it will be automatically invoked when an instance of the class is created. A class may contain at least one constructor declaration. If a class has no constructor, a constructor is provided automatically. A class can have any number of constructors. When you are using the attribute public or private with constructor parameters, a field is automatically created, which is assigned the value.
Syntax
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constructor(ParameterList(Optional)) { ................//body} |
The following example tells you, how to use a constructor in TypeScript. Use the following procedure to create a program using a constructor.
Step 1
Open Visual Studio 2012 and click on "File" menu -> "New" -> "Project". A window will be opened. Specify the name of your application, like "ExampleOfConstructor". Your application will look like:
![constructor1-in-TypeScript.jpg]()
Then click on the OK button.
Step 2
After Step 1 your project has been created. The Solution Explorer, which is at the right side of Visual Studio, contains the js file, ts file, css file and html files.
Step 3
The code of Constructor program:
ExampleOfConstructor.ts
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class MyExample {
public Fname: string;
public Lname: string;
constructor (Fname: string, Lname: string) {
this.Fname = Fname;
this.Lname = Lname;
alert("Company name="+this.Fname+" "+this.Lname);
}
}
window.onload = () =>
{
var data = new MyExample ("Mcn","Solution");
} |
Note In the above declared program, I have the MyExample class, with a constructor which takes two string value as arguments. When I create an instance of the class (MyExample), the constructor is automatically executed.
default.html
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<!DOCTYPEhtml>
<htmllang="en"xmlns="http://www.w3.org/1999/xhtml">
<head>
<metacharset="utf-8"/>
<title>TypeScript HTML App</title>
<linkrel="stylesheet"href="app.css"type="text/css"/>
<scriptsrc="app.js"></script>
</head>
<body>
<h1>Example of Constructor</h1>
<divid="content"/>
</body>
</html> |
app.js
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var MyExample = (function () {
function MyExample(Fname, Lname) {
this.Fname = Fname;
this.Lname = Lname;
alert("Company name=" + this.Fname + " " + this.Lname);
}
return MyExample;
})();
window.onload = function () {
var data = new MyExample("Mcn","Solution");
}; |
Output:
![constructor2-in-TypeScript.jpg]()