↑
Main Page

getServerInfo

setTimeout(function () {

frames[“hiddenFrame”].location.href = “HiddenFrameExampleCom2.htm”;

}, 10);

}

The first change is the addition of a global variable names

oHiddenFrame

. Because the same frame can

be used repeatedly for requests, there’s no reason to keep creating new iframes for each request. Instead,

this global variable holds a reference to the iframe when it’s created. When

getServerInfo()

is called,

it first checks to see if an iframe already exists by checking the value of

oHiddenFrame

. If it doesn’t exist,

the frame is created using the DOM

createElement()

method.

Creating the iframe using the DOM is very specific. Both the

name

and

attribute must be set to equal

“hiddenFrame”

in order for this to work in most browsers (some require

name

to be set, others require

). Next, the appearance of the frame is specified to have a height and width of

, an absolute position,

and visibility set to

“hidden”

. All these changes are necessary to ensure that this new addition to the

document doesn’t disrupt the display. Lastly, the iframe is added to the document body.

When the iframe has been created and added, it takes most browsers (notably Mozilla and Opera) a cou-

ple of milliseconds to recognize it as a new frame in the

frames

collection. To take this into account, the

setTimeout()

function is used to create a wait of 10 milliseconds before the request is sent. By the time

the request executes, the browsers recognizes the new frame, and it’s sent off without a hitch.

The only modification necessary to the page providing the response is to use

parent

instead of

parent.frames[0]

to call

handleResponse()

<html>

<head>

<title>Hidden Frame Example (Response)</title>

window.onload = function () {

parent.handleResponse(document.forms[“formResponse”].result.value);

};

</script>

</head>

<body>

<textarea name=”result”>This is some data coming from the

server.</textarea>

</form>

</body>

</html>

Now calling

getServerInfo()

has the exact same effect as the previous example using the traditional

hidden frame technique. This technique requires, of course, that the browser support iframes in the first

place, which leaves older browsers like Netscape Navigator 4.x out of the loop.

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