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Javascript: More Loops and Events


In our last tutorial we covered functions and a portion of loops, leaving off at the While loop. In this tutorial we will continue with the Do While Loop and hopefully work our way through to a taste of JavaScript Events.

Author Info:
By: James Payne
Rating: 4 stars4 stars4 stars4 stars4 stars / 4
November 14, 2007
TABLE OF CONTENTS:
  1. · Javascript: More Loops and Events
  2. · Break Dancing
  3. · And So it Continues
  4. · Finishing Loops

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Javascript: More Loops and Events - Finishing Loops
(Page 4 of 4 )

For...In...Er

Remember that band? I don't. I mean, what songs did they play? Oh yeah, you are right. Hot Blooded, Head Games, and who can forget Cold as Ice? I guess I can, actually. What did they have, a temperature fetish?

For...In is another way to loop. You use it when you want to loop though the values held in an array. I know we haven't covered arrays yet, but we will. For now just know that arrays are similar to boxes, like variables are. Except that where variables hold one value, arrays hold many values. Sort of like a box full of variables.

You can also use the For...In on variables and objects (we will discuss these later as well). For now though, let's loop through that array.


<html>

<body>

<script type="text/javascript">

var dogs

var mydogs = new Array()

mydogs[0] = "Linus"

mydogs[1] = "Charlie"

mydogs[2] = "Violet"

mydogs[3] = "Molly Volly"

mydogs[4] = "Sally Anne"

mydogs[5] = "Lucy (RIP)"

mydogs[6] = "Schroeder (Enjoy the new home)"

for (dogs in mydogs)

{

document.write(mydogs[dogs] + "<br />")

}

</script>

</body>

</html>

You can tell several things from the above code: 1) I have too many dogs 2) I named them all after Peanuts characters (Molly Volly is Snoopy's tennis instructor) and 3) If I have any say in it (which I don't) my next dog will be named Pigpen.

Aside from that, here is how the program works. We create a variable named dogs, then an array named mydogs. We then assign the array 7 values (0 is the first value in the array). The values are my dogs' names. We then use the For...In statement to loop through the array and finally print out the values. Note that the For...In line is the one that says: for (dogs in mydogs)

That is it for our coverage of loops. In an entirely new series on JavaScript we will discuss Events, which allow the user to trigger certain things within a browser. They help provide a truly interactive experience and are fun to work with. As I sometimes do, I am going to leave you with a table listing the various Events.


Event

Trigger

Onabort

Occurs when the loading of an image is interrupted

OnBlur

Occurs when an element loses focus

OnChange

Occurs when the user changes a field

OnClick

Occurs when a user's mouse clicks an object

OndblClick

Occurs when user double-clicks an object

OnError

Occurs when an error happens while loading a document or an image

OnFocus

Occurs when an element has focus

OnKeyDown

Occurs when a key on the keyboard is pressed

OnKeyPress

Occurs when a key on a keyboard is pressed or held down

OnKeyUp

Occurs when a keyboard key is released

OnLoad

Occurs when a page or an image finishes loading

OnMouseDown

Occurs when a mouse button is pressed

OnMouseMove

Occurs when a mouse is moved

OnMouseOut

Occurs when a mouse if moved off of an element

OnMouseOver

Occurs when a mouse is moved onto an element

OnMouseUp

Occurs when a mouse button is released

OnReset

Occurs when the reset button is clicked

OnResize

Occurs when a window or frame is resized

OnSelect

Occurs when text is Selected

OnSubmit

Occurs when the submit button is clicked

OnUnLoad

Occurs when the user exits the page

Beautiful ain't it?

Till then...


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