Extending native JavaScript objects with Object.create
I've been reading Inheritance and the prototype chain on the Mozilla Developer Network and have been wondering about something it said.
One mis-feature that is often used is to extend Object.prototype or one of the other built-in prototypes.
I understand why adding a new function onto a native object's prototype would cause issues.
Array.prototype.first = function() { return this[0]; };
But suppose someone created a new array and wanted it to have all the functionality of Array via its prototype chain, and they did something like this:
function MyArray() { Array.apply(this, arguments); }
MyArray.prototype = Object.create(Array.prototype);
MyArray.prototype.first = function() { return this[0]; };
Is this method of extending (inheriting from) a native object also considered bad practice? If so, what problems would it cause?
This is a general software architecture question, so there can be a lot of different perspectives on what is right or wrong.
My opinion is that native objects should stay native objects. If I were an outsider looking at a code base with a native object being modified, I would be very confused. I could be a javascript guru, but I would be lost and confused at first.
A better way of doing the exact same thing, is instead of extending through inheritance, to extend through composition.
function ListClass() {
var arr = [];
return {
first: function() { return arr[0]; },
get: function(i) { return arr[i]; },
push: arr.push
};
}
Your idea is completely valid javascript. The only objection would be code clarity.
链接地址: http://www.djcxy.com/p/27242.html