问题
I would like to extend the existing XMLHttpRequest object so that it should work with all the browsers. Now i have been trough with JS inheritance and things however before starting i would like to see good example of it.
HTML5 has upload and progress events stuff which i would like to implement in inherited new object which can behave even if the feature is not supported by not introducing JS errors to client side. so i would like to achieve something like this.
Class XMLHttpRequest{}
Class UploadXMLHttpRequest: XMLHttpRequest{}
Where additional methods can be attached to UploadXMLHttpRequest class like following.
UploadXMLHttpRequest.prototype.uploadFile = function(file){
}
Considering YUI, JQuery and others are good in market no one really wants to do this made it little difficult for me to find good resources.
回答1:
Don't do this. XMLHttpRequest is a host object and you should not try to extend it. To quote Kangax:
Next problem with DOM extension is that DOM objects are host objects, and host objects are the worst bunch. By specification (ECMA-262 3rd. ed), host objects are allowed to do things, no other objects can even dream of. To quote relevant section [8.6.2]:
Host objects may implement these internal methods with any implementation-dependent behaviour, or it may be that a host object implements only some internal methods and not others.
This also means that host objects may disallow extension by using prototype.
However, as Kangax also advices, you can create a wrapper around XMLHttpRequest and do whatever you like with it.
来源：https://stackoverflow.com/questions/4931977/how-to-extend-xmlhttprequest-object-in-javascript