JavaScript by Example: JavaScript Core Objects. Pt. 2

Properties of the Function object.

Property

What It Does

length

Returns the number of arguments that are expected to be passed (read only)

prototype

Allows the object to be customized by adding new properties and methods

Methods of the Function object.

Property

What It Does

apply()*

Allows you to apply a method from one function to another

call()

Allows you to call a method from another object

* Supported on versions Netscape 4.06+ and Internet Explorer 5.5+.

var nameOfFunction = new Function (arguments, statements_as_string: }

Example Function Definition:

var addemUp = new Function ( "a", "b", "return a + b;" );

Example Function Call:

document.write(addemUp (10, 5));

<html><head><title>Function Object</title>

</head>

Anonymous Functions and the Function Constructor<p>

1 var sum = new Function("a","b", "return a + b; ");

2 window.onload = new Function ( "document.bgColor='yellow';");

3 document.write( "The sum is " + sum(5,10)+ "<br>");

document.write( "The background color is yellow<br>");

</script>

</body></html>


A variable called sum is a Function object, created by the Function() constructor. It has two arguments, "a" and "b". The function statements are the last string in the list. These statements will be executed when the function is called.
This Function() constructor only has one argument, the statement that will be executed when the function is called. Since the function is assigned to the onload event method for the window object, it will act as an event handler and cause the background color to be yellow when the document has finished loading. The sum function is called with two arguments. (See Figure 9.32.)

A variable called sum is a Function object, created by the Function() constructor. It has two arguments, "a" and "b". The function statements are the last string in the list. These statements will be executed when the function is called.

This Function() constructor only has one argument, the statement that will be executed when the function is called. Since the function is assigned to the onload event method for the window object, it will act as an event handler and cause the background color to be yellow when the document has finished loading.
The sum function is called with two arguments. (See Figure 9.32.)


<html><head><title>The with Keyword</title> </head> <body> <h2>Using the <em>with</em> keyword</h2> <p> <h3> <script language="JavaScript"> var yourname=prompt("What is your name? ",""); // Create a string object with(yourname){ document.write("Welcome " + yourname + " to our planet!!<br>"); document.write("Your name is " + length + " characters in length.<br>"); document.write("Your name in uppercase: " + toUpperCase() + ".<br>"); document.write("Your name in lowercase: " + toLowerCase() + ".<br>"); } </script> </h3> </body></html>

<html><head><title>The with Keyword</title>

</head>

<body>

<h2>Using the <em>with</em> keyword</h2>

<p>

<h3>

var yourname=prompt("What is your name? ","");

// Create a string object

with(yourname){

document.write("Welcome " + yourname + " to our planet!!<br>");

document.write("Your name is " + length + " characters in

length.<br>");

document.write("Your name in uppercase: " + toUpperCase() +

".<br>");

document.write("Your name in lowercase: " + toLowerCase() +

".<br>");

}

</script>

</h3>

</body></html>

1. Creating a multidimensional array (i.e., an array with more than one index) is not officially supported by JavaScript, but can be simulated with some trickery.

2. Arrays were introduced in JavaScript 1.1.

3. For more information about the time and date, see http://www.timeanddate.com/worldclock/.

4. Greenwich Mean Time (GMT) is now called Universal Coordinate Time (UTC). The current time in Greenwich, England is five hours + New York's present time, or eight hours + San Francisco's present time.

5. These methods are part of the ECMA 3.0, IE5.5+, Netscape 6.0+.