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JavaScript - Prototypes
Can somebody please link me to a good guide or tutorial for prototypes?
Thanks Similar TutorialsHi all, The result of the code below is slightly surprising to me. If you define an object type through a prototype, and that object has a property which is a hash, the value of that hash is shared between all instances of that type. I understand the way around this (e.g. define "myHash" as its own object, and call this.myHash = new MyHash() in the object's constructor), but can someone describe to me exactly why the property "a" and the property "myHash" behave differently in the example below? Code: var MyType = function() {}
MyType.prototype = {
a: null,
myHash: {
b: null
}
}
var instance1 = new MyType();
var instance2 = new MyType();
instance1.a = "a1";
instance2.a = "a2";
instance1.myHash.b = "b1";
instance2.myHash.b = "b2";
alert(instance1.a); // = "a1"
alert(instance1.myHash.b); // = "b2"
Thanks! In the spirit of the season, I wanted to make it snow on my website. So I began digging. Eventually I ended up with a script that moved an image element down the page in a snowflake-like manner. The problem with it was it was dependant on an img element for every flake - simply no poor programming when using an Object Oriented programming language. So I decided I wanted to extend (in Java-speak; most of my programming background is in Java) the in-built Image object. The new object's src variable will lead to an image of the type of flake it is. (I want to be able to have more variance in images than a simple dot.) The new object will have a function that will allow it to move. A separate, unrelated function will control when each flakes move. I did some more research and read about prototyping on JavaScript Kit and here, but I still cant seem to get this to work. JS Lint says it's bug-free, but Firefox says "move()" is an invalid function. I am presuming the problem lies in my inability to fully grasp how to extend objects in JavaScript. Code: <html>
<head>
<script type="text/javascript">
Image.prototype.dFlake=dotFlake;
function dotFlake(xLocation,yLocation){
this.src = "simpleDotFlake.png";
this.x = xLocation;
this.y = yLocation;
}
dotFlake.prototype.move = fall;
function fall(){ // ^^ Belongs to dotFlake class.
this.style.position="absolute";
this.style.top = this.y;
this.style.left = this.x;
this.y= this.y + 1; // Falling is constant.
if (Math.random() > 0.5){ // Random direction, though.
this.x = this.x + 1;
} else{
this.x = this.x - 1;
}
}
function snow(flakes){ // Allows addition of different flakes later.
for (i in flakes){
i.move();
}
timer = setTimeout("snow()",1);
}
function startSnow(){
basicFlakes = new Array(new dotFlake(0,0));
snow(basicFlakes);
}
</script>
</head>
<body onload="startSnow()">
<h1>This is test text.</h1>
<img id="basicFlake" src="./simpleDotFlake.png" width="10" height="10" />
</body>
</html>
Any and all input is much appreciated. Thank you! Hey, I am using prototypes (library) ajax methods and one of them is properties. I am passing in the name value pairs: var itemFilter = "MajorCat: Shoes", parameters: { q : qry ,fq: itemFilter }, But when I request, it gives me this in the url: MajorCat%3AShoes That won't work, the search application on the backend doesn't filter properly because of the "%3A" instead of ":". When I manually pass in via the url: MajorCat: Shoes (at the end of the query) it works. So, that ":" is getting encoded. How do I get that IN the hash and make sure the request is unencoded when it goes out? thanks |
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