The "Function" Object Type - Functions Are Objects

This section provides a quick description and a tutorial example script on the 'Function' built-in object type, which is used to create functions.

The "Function" object type is a special built-in object type to be used to create new functions. It has the following main features:

function [function_name](parameter_1, parameter_2, ...) { statement_1; statement_2; ... return return_expression };

Here is a tutorial example script showing some of the those features:

// Function_Object_Type.js
// Copyright (c) 2013 by Dr. Herong Yang, herongyang.com

   // Creating a new function with the "Function()" constructor
   var sign = new Function("name",
      "this.signature = name;"
      + "sign.count++;"
   )
   
   // Adding an instance property to the function
   sign.count = 0;

   // Checking this object
   println("\nAbout this \"sign\":");
   println("   Type = "+(typeof sign));
   println("   Instance Of Object: "+(sign instanceof Object));
   println("   Instance Of Function: "+(sign instanceof Function));

   // Executing it on the current object
   sign("Herong");

   // Calling it on another object
   var pc = new Object();
   sign.call(pc, "IBM");

   // Checking the signature
   println("\nExecution result:");
   println("   this.signature = " + this.signature);
   println("   pc.signature = " + pc.signature);
   println("   # of calls = " + sign.count);

If you run this script with "jrunscript", you will get:

About this "sign":
   Type = function
   Instance Of Object: true
   Instance Of Function: true

Execution result:
   this.signature = Herong
   pc.signature = IBM
   # of calls = 2

Now we know how to create functions with the "Function()" constructor.

Read other "Function" related chapters to see more tutorial examples.

Table of Contents

 About This Book

 Introduction to JavaScript

 ECMAScript Language Specification and JavaScript Dialects

 Data Types, Variables and Expressions

 Flow Control Statements

 Creating, Accessing, and Manipulating Arrays

 Defining and Calling Functions

 Web Browser Supporting JavaScript

 Server-Side and Client-Side Web Scripting

 Introduction to Objects

 Defining Your Own Object Types

 Inheritance of Properties and Methods through the Prototype Object Chain

 'jrunscript' - JavaScript Shell Command from JDK

 Using Functions as "Function" Objects

Introduction to Built-in Object Types

 Overview of Built-in Object Types

 The "Object" Object Type - The Root Object Type

 The "Global" Object Type - The Invisible Global Container

 Global Properties and Functions Defined in ECMAScript

 Global Properties and Functions Provided by "jrunscript"

The "Function" Object Type - Functions Are Objects

 The "Array" Object Type - Arrays Are Objects

 The "String" Object Type - Not Equal to String Primitive Type

 The "Boolean" Object Type - Wrapping Boolean Values into Objects

 The "Number" Object Type - Not Equal to Number Primitive Type

 The "Date" Object Type - Managing Dates and Times

 The "RegExp" Object Type - Regular Expression Patterns

 The "Error" Object Type - Runtime Exceptions

 The "Math" Object Type - The Math Container

 W3C's Document Object Model (DOM) Specifications

 References

 PDF Printing Version