<div class="intro">
<p>This example demonstrates how to use multiple NodeList features to build a simple game.</p>
</div>
<div class="example">
{{>ducks-source}}
</div>
<h2>The HTML</h2>
```
{{>ducks-html}}
```
<h2>YUI Instance</h2>
<p>
The `use` statement doesn't include `node` because it's loaded as a requirement of transition.
</p>
```
YUI().use('transition', 'button', function(Y){
// code goes here
});
```
<h2>Setting Vars</h2>
<p>
The variable `ducks` is used for easily manipulating all the ducks at once.
We'll display various duck comments from the array `squawkTextArr` on a rotating basis.
</p>
```
var ducks = Y.all('.duck-row li'),
ducksRemaining = 10, // value for UI display
squawkTextIndex = 0, // index in the squawkTextArr to use next
squawkTextArr = [ // duck comments
'#@&~*Q!',
'Hey!?',
'911 on U!',
"U fly's down",
'duck pile!',
'Ricochets kill!',
'how sporting.',
"shoe's untied"
];
```
<h2>Initializing the Ducks</h2>
<p>
Repetitive markup is added with the `.append()` method to all the ducks in the `NodeList`.
This keeps the original markup simple and clear.
</p>
```
// append the same content for each duck <li>
ducks.append('<img src="../assets/node/images/duck.png"/><div class="squawk"><div class="text">#@&~*Q!</div><div class="small-squawk-bubble"></div></div>');
```
<p>
All the ducks in the `NodeList` are given the `set-up` class with the `.addClass()` method.
This class is found on any duck that has the state of being set up, as opposed to being knocked down.
</p>
```
// give them all the set-up state class
ducks.addClass('set-up');
```
<p>
This state could be a Boolean property, but it's handy as a class,
because a `NodeList` can be made containing the squawks of all "set up" ducks in this way,
`squawks = Y.all('.duck-row .set-up .squawk');`
as we'll see in the `makeDucksSquawk` function.
</p>
<h2>Making the Ducks Swim</h2>
<p>
This uses `transition` to make the ducks swim right to left
</p>
```
// this makes the ducks move from right to left.
// When the duck on the far left disappears from view,
// it's added to the far right end of the row.
var makeDucksSwim = function () {
var frontDuck;
// move the duck row to the left one duck space over 2 seconds
Y.one('.duck-row').transition({
easing: 'linear',
left: '-119px',
duration: 2
}, function () { // when the row finishes its right to left transition...
// remove the first duck on the left
// which has trasitioned out of view
frontDuck = Y.one('.duck-row li').remove();
// append the removed first duck onto the right end
Y.one('.duck-row').appendChild(frontDuck);
// set the position for the next makeDucksSwim()
Y.one('.duck-row').setStyle('left', '10px');
// if there are ducks remaining, make them swim again
if (ducksRemaining > 0) {
makeDucksSwim();
}
});
}
makeDucksSwim(); // this initializes the ducks swimming
```
<h2>Click Event Handler</h2>
<p>
</p>
```
// handles a click on a duck
var duckClick = function(e) {
var squawks;
// remove the squawk belonging to the duck that was clicked
e.currentTarget.one('.squawk').setStyles({'top': '-400px', 'opacity': '1'});
// makes the ducks appear to lay back when clicked
duration: 0.2,
height: '3px',
width: '133px'
});
// the clicked duck will no longer have the 'set-up' class/state
e.currentTarget.removeClass('set-up');
makeDucksSquawk(); // makes the ducks squawk
updateDucksRemaining(); // update the number of ducks still set up
};
```
<h2>Squawking Ducks</h2>
<p>
</p>
```
// this makes the duck's squawks show and hide and get various text
var makeDucksSquawk = function(){
squawks = Y.all('.duck-row .set-up .squawk'); // a NodeList of the squawks of set-up ducks
if (Y.one('#show-attitude')._node.checked) { // only have ducks squawk if the checkbox is checked
// fill voice bubbles with next text string
Y.all('.duck-row .set-up .squawk .text').setContent(squawkTextArr[squawkTextIndex]);
// increment the index to get the next squawk text
squawkTextIndex = (squawkTextIndex += 1) % (squawkTextArr.length);
top: {
delay: 0.5,
value: '0px', // drop squawks into position from hidden
duration: 0 // instant position change
},
opacity: { // fade out
delay: 3.0,
duration: 0.3,
value: 0
}
}, function(e){
// after squawks are faded out,
// move them to hidden position and set opacity to 1 again
squawks.setStyles({'top': '-400px', 'opacity': '1'});
});
}
}
```
<h2>Reset and Ducks Remaining</h2>
```
// This resets all ducks, "ducks remaining" counters, and row position
// make the duck images full height
// start them swimming
var reset = function() {
Y.all('.duck-row li img').setStyle('height', '55px');
Y.all('.duck-row li').addClass('set-up');
updateDucksRemaining();
makeDucksSwim();
}
// counts the ducks remaining, and updates the UI counter display
var updateDucksRemaining = function() {
Y.one('.ducks-remain').setContent(ducksRemaining);
}
```
<h2>Prefer `node.delegate()` over `nodelist.on()`</h2>
<p>Sometimes you need to create individual subscriptions for each Node in a
NodeList, but usually it's preferable to use
<a href="node-evt-delegation.html">event delegation</a> as shown in this example.</p>
<h2>Listeners</h2>
<p>
</p>
```
// listeners
Y.one('.duck-row').delegate('click', duckClick, 'li');
Y.one('#button-reset').on('click', reset);
```
<h2>Complete Ducks Example Source</h2>
```
{{>ducks-source}}
```