I need an array to store some geometrical data. I would like to simply inherit from the Array object and than extend it with a few new functions like "height" and "width" (sum of all children's heights/widths), but also with a few convenience methods like "insertAt" or "remove".
What is the best way to do it without modifying the original Array object (Array.prototype.myMethod)?
You can always mixin your changes directly into Array, but that might not be the best choice given that it's not something every array should have. So let's inherit from Array:
// create a constructor for the class
function GeometricArray() {
this.width = 0;
this.height = 0;
}
// create a new instance for the prototype so you get all functionality
// from it without adding features directly to Array.
GeometricArray.prototype = new Array();
// add our special methods to the prototype
GeometricArray.prototype.insertAt = function() {
...
};
GeometricArray.prototype.remove = function {
...
};
GeometricArray.prototype.add = function( child ) {
this.push( child );
// todo calculate child widths/heights
};
Are you (maybe) applying Java concepts to Javascript?
You don't need to inherit from classes in Javascript, you just enrich objects.
So the best way in my world (a world full of people head-butting methods into objects) is:
function GeometricArray()
{
var obj=[]
obj.height=function() {
// wibbly-wobbly heighty things
for(var i=0;i<this.length;i++) {
// ...
}
}
obj.width=function() {
// wibbly-wobbly widy things
// ...
}
// ...and on and on...
return obj
}
prototype and this are all part of a what the new operator does in javascript. It's an overthought with little to no point in existing as long as you are the one that writes the constructor.Array or Object. In that case you cannot override the constructor, but using prototype you can enrich those objects anyway. (only, it came out, it's really easy to shoot yourself in a foot this way) I'm not up to date on that, but I suppose some browser could treat enriching of some core objects like a security threatYou could use prototyping to put those functions in Array.
To add the height function for example do this:
Array.prototype.height = function() {
//implementation of height
}
