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我想創建一個只接受要存儲的特定實例類型的數組。看起來最好的解決方案是使用Proxies，受此啓發gist和SO thread。使用JS代理拒絕數組輸入
所以我有一個代理工作，併爲基本的數組功能，它按預期工作。 set屬性確保只有對象是水果的實例才能插入數組，否則會引發TypeError。唯一可以立即設置的其他財產是length。
問題在於高級I/O，如splice()。記錄set函數顯示數組項目被移位以爲要在[0]處插入的新項目留出空間，但是當新項目被拒絕時，它將數組置亂。
由於set被稱爲迭代，我沒有看到一個明確的方法來阻止拼接啓動，或恢復數組在代理內的前榮耀（最好是前一種選擇）。其他人是否知道如何實現這些想法或者有其他建議？
"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);
數組沒有[[Call]]方法。你的'應用'陷阱是沒用的。 – Oriol
我想你會更好地擴展'Array'原型，重新定義可能會改變陣列的新原型的所有方法。 – trincot
@trincot這是我的第一個想法，它工作得很好，直到重載[]速記。 –