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History

Here, the code uses linked timeouts, meaning that the code being executed by

setTimeout()

also calls

setTimeout()

. If

iNum

is still not equal to

iMax

after it is incremented, another

setTimeout()

call is

made. You don’t have to keep track of the timeout ID or clear it because after the code is executed, the

timeout ID is destroyed.

History

It is possible to access the history of a browser window. The history is the list of places the user has been.

For security reasons, all you can do is navigate through the history; there is no way to get the URLs of

the pages contained in the browser history.

To navigate through history, you don’t need a time machine; you use the

window

object’s

history

prop-

erty and its associated methods.

The

go()

method takes only one parameter: the number of pages to go back or forward. If the number is

negative, you are going backwards through the browser history. If the number is positive you are going

forward (think of it as the difference between the Back and Forward buttons).

So, to go back one page, the following code can be used:

window.history.go(-1);

Of course, the reference to the

window

object isn’t necessary, so this will do:

history.go(-1);

Most often, this is used to create a custom “Back” button embedded in a Web page, such as:

<a href=”javascript:history.go(-1)”>Back to the previous page</a>

To go forward one page, just use a positive one:

history.go(1);

Alternatively, you can use the

back()

and

forward()

methods to accomplish the same thing:

//go back one

history.back();

//go forward one

history.forward();

These may be a little more meaningful because they accurately reflect the behavior of the browser Back

and Forward buttons.

So which method should you use? It’s really depends on the use case. To wait a cer-

tain amount of time before executing a certain set of code, use timeouts. If, however,

you need some code to be executed repeatedly, then use intervals.

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