Instantly share code, notes, and snippets.

@ElGoorf /proxy.js
Last active Dec 17, 2016

Embed
What would you like to do?
Using Proxy and Reflect (ES6) to restrict insertion of objects into an Array - with test
"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([], {
deleteProperty: function(target, property) {
return true;
},
set: function(target, property, value, receiver) {
//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+")");
}
}
}
});
Reflect.defineProperty(fruitbowl, 'splice', {
configurable: true,
enumerable: false,
value: function(start, deleteCount, ...items) {
if (items.every(item => item instanceof Fruit)) {
return Reflect.apply(Array.prototype.splice, this, [start, deleteCount, ...items]);
} else {
throw new Error('All elements must be Fruit objects');
}
}
});
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");
}
console.log("Fruitbowl should still be empty: " + (fruitbowl.length == 0 ? "PASSED" : "FAILED"));
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");
try{
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+")"));
fruitbowl.splice(0,0,new Fruit("pineapple"));
console.log("Should now have 3 fruit: " + (fruitbowl.length == 3 ? "PASSED" : "FAILED"));
console.log("Should first fruit should be pineapple: " + (fruitbowl[0].name == "pineapple" ? "PASSED" : "FAILED"));
fruitbowl.splice(1,1);
console.log("Should now have 2 fruit: " + (fruitbowl.length == 2 ? "PASSED" : "FAILED"));
console.log("Should first fruit should be pineapple: " + (fruitbowl[0].name == "pineapple" ? "PASSED" : "FAILED"));
console.log("Should second fruit should be banana: " + (fruitbowl[1].name == "banana" ? "PASSED" : "FAILED"));
console.log("Should third fruit should be non-exostant: " + (typeof(fruitbowl[2] )== "undefined" ? "PASSED" : "FAILED"));
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment