在javascript中扩展Array对象的方法 [英] Ways to extend Array object in javascript
问题描述
我尝试使用一些用户友好的方法(例如 Array.Add() 而不是 Array.push() 等)在 javascript 中扩展 Array 对象...
i try to extend Array object in javascript with some user friendly methods like Array.Add() instead Array.push() etc...
我实现了 3 种方法来做到这一点.不幸的是,第三种方式不起作用,我想问一下为什么?以及如何做到这一点.
i implement 3 ways to do this. unfortunetly the 3rd way is not working and i want to ask why? and how to do it work.
//------------- 1st way
Array.prototype.Add=function(element){
this.push(element);
};
var list1 = new Array();
list1.Add("Hello world");
alert(list1[0]);
//------------- 2nd way
function Array2 () {
//some other properties and methods
};
Array2.prototype = new Array;
Array2.prototype.Add = function(element){
this.push(element);
};
var list2 = new Array2;
list2.Add(123);
alert(list2[0]);
//------------- 3rd way
function Array3 () {
this.prototype = new Array;
this.Add = function(element){
this.push(element);
};
};
var list3 = new Array3;
list3.Add(456); //push is not a function
alert(list3[0]); // undefined
在第三种方式中,我想在内部扩展 Array 对象 Array3 类.如何做到这一点才不会出现推送不是函数"和未定义"?
in 3rd way i want to extend the Array object internally Array3 class. How to do this so not to get "push is not a function" and "undefined"?
这里我添加了第四种方式.
Here i add a 4th way.
//------------- 4th way
function Array4 () {
//some other properties and methods
this.Add = function(element){
this.push(element);
};
};
Array4.prototype = new Array();
var list4 = new Array4();
list4.Add(789);
alert(list4[0]);
这里我又必须使用原型.我希望避免在类构造函数之外使用额外的行作为 Array4.prototype.我想要一个紧凑的定义类,所有部分都集中在一个地方.但我想我不能这样做.
Here again i have to use prototype. I hoped to avoid to use extra lines outside class constructor as Array4.prototype. I wanted to have a compact defined class with all pieces in one place. But i think i cant do it otherwise.
推荐答案
方法名应该小写.不应在构造函数中修改原型.
Method names should be lowercase. Prototype should not be modified in the constructor.
function Array3() { };
Array3.prototype = new Array;
Array3.prototype.add = Array3.prototype.push
在 CoffeeScript 中
in CoffeeScript
class Array3 extends Array
add: (item)->
@push(item)
如果您不喜欢这种语法,并且必须从构造函数中扩展它,您唯一的选择是:
If you don't like that syntax, and you HAVE to extend it from within the constructor, Your only option is:
// define this once somewhere
// you can also change this to accept multiple arguments
function extend(x, y){
for(var key in y) {
if (y.hasOwnProperty(key)) {
x[key] = y[key];
}
}
return x;
}
function Array3() {
extend(this, Array.prototype);
extend(this, {
Add: function(item) {
return this.push(item)
}
});
};
你也可以这样做
ArrayExtenstions = {
Add: function() {
}
}
extend(ArrayExtenstions, Array.prototype);
function Array3() { }
Array3.prototype = ArrayExtenstions;
在过去,'prototype.js' 曾经有一个 Class.create 方法.你可以把所有这些都包装成这样的方法
In olden days, 'prototype.js' used to have a Class.create method. You could wrap all this is a method like that
var Array3 = Class.create(Array, {
construct: function() {
},
Add: function() {
}
});
有关此以及如何实现的更多信息,请查看prototype.js 源代码
For more info on this and how to implement, look in the prototype.js source code
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