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我想创建一个只接受要存储的特定实例类型的数组。看起来最好的解决方案是使用Proxies，受此启发gist和SO thread。使用JS代理拒绝数组输入
所以我有一个代理工作，并为基本的数组功能，它按预期工作。 set属性确保只有对象是水果的实例才能插入数组，否则会引发TypeError。唯一可以立即设置的其他财产是length。
问题在于高级I/O，如splice()。记录set函数显示数组项目被移位以为要在[0]处插入的新项目留出空间，但是当新项目被拒绝时，它将数组置乱。
由于set被称为迭代，我没有看到一个明确的方法来阻止拼接启动，或恢复数组在代理内的前荣耀（最好是前一种选择）。其他人是否知道如何实现这些想法或者有其他建议？
"use strict";
class Fruit {
constructor(name) {
this._name = name;
}
set name(name) {
this._name = name;
}
get name() {
return this._name;
}
}
class Vegetable {
constructor(name) {
this.name(name);
}
set name(name) {
this._name = name;
}
get name() {
return this._name;
}
}
// a proxy for our array
var fruitbowl = new Proxy([], {
apply: function(target, thisArg, argumentsList) {
return thisArg[target].apply(this, argumentList);
},
deleteProperty: function(target, property) {
console.log("Deleted %s", property);
return true;
},
set: function(target, property, value, receiver) {
// UNCOMMENT HERE for useful output:
// console.log("Setting " + property + " to ", value);
if (property == "length") {
target.length = value;
return true;
} else {
if (value instanceof Fruit) {
target[property] = value;
return true;
} else {
return false;
// throw TypeError("Expected Fruit, got " + typeof(value) + " (" + value + ")");
}
}
}
});
console.log("\n\n=== Putting fruit into the bowl... ===\n\n");
try {
fruitbowl.push(new Vegetable("potato"));
} catch (e) {
console.log("Shoudln't allow vegetables: PASSED");
}
fruitbowl.push(new Fruit("apple"));
console.log("Should allow fruit: " + (fruitbowl.length == 1 ? "PASSED" : "FAILED"));
fruitbowl[0] = new Fruit("orange");
console.log("Should replace item specified as long as it's a Fruit: " + (fruitbowl.length == 1 && fruitbowl[0].name == "orange" ? "PASSED" : "FAILED"));
try {
fruitbowl[0] = "Bananas!!1one";
} catch (e) {
}
console.log("Should not replace with a string: " + (fruitbowl.length == 1 && fruitbowl[0].name == "orange" ? "PASSED" : "FAILED"));
fruitbowl.push(new Fruit("banana"), new Fruit("pear"));
console.log("Should have 3 items [orange, banana, pear]: " + (fruitbowl.length == 3 ? "PASSED" : "FAILED"), fruitbowl);
console.log("\n\n === Cropping the bowl... ===\n\n");
fruitbowl.length = 2;
console.log("Should have 2 items [orange,banana]: " + (fruitbowl.length == 2 ? "PASSED" : "FAILED"));
console.log("Should error at item 2: " + (!fruitbowl[2] ? "PASSED" : "FAILED"), fruitbowl);
console.log("\n\n === Splicing the bowl... ===\n\n");
console.log(fruitbowl.length);
try {
console.log(fruitbowl.length);
fruitbowl.splice(0, 0, "pineapples!!1one");
console.log(fruitbowl.length);
} catch (e) {
console.log("Shouldn't have inserted string: PASSED");
}
console.log("Should still only have 2 fruit: " + (fruitbowl.length == 2 ? "PASSED" : "FAILED (" + fruitbowl.length + ")"));
console.log(fruitbowl);
数组没有[[Call]]方法。你的'应用'陷阱是没用的。 – Oriol
我想你会更好地扩展'Array'原型，重新定义可能会改变阵列的新原型的所有方法。 – trincot
@trincot这是我的第一个想法，它工作得很好，直到重载[]速记。 –