在 Javascript 中观察数组的变化是相对简单的。
我使用的一种方法是这样的:
// subscribe to add, update, delete, and splice changes
Array.observe(viewHelpFiles, function(changes) {
// handle changes... in this case, we'll just log them
changes.forEach(function(change) {
console.log(Object.keys(change).reduce(function(p, c) {
if (c !== "object" && c in change) {
p.push(c + ": " + JSON.stringify(change[c]));
}
return p;
}, []).join(", "));
});
});
但是,我最近读到
Array.observe
已弃用,我们应该使用 proxy object instead.我们如何检测 Proxy 对象数组的变化?我找不到任何例子,有人有兴趣详细说明吗?
最佳答案
从我可以从 MDN page 中读到的内容,您可以创建一个通用处理程序,您可以在其中处理对任何对象的所有更改。
从某种意义上说,您编写了一个拦截器,每次您从数组中获取值或设置值时都会进行干预。然后,您可以编写自己的逻辑来跟踪更改。
var arrayChangeHandler = {
get: function(target, property) {
console.log('getting ' + property + ' for ' + target);
// property is index in this case
return target[property];
},
set: function(target, property, value, receiver) {
console.log('setting ' + property + ' for ' + target + ' with value ' + value);
target[property] = value;
// you have to return true to accept the changes
return true;
}
};
var originalArray = [];
var proxyToArray = new Proxy( originalArray, arrayChangeHandler );
proxyToArray.push('Test');
console.log(proxyToArray[0]);
// pushing to the original array won't go through the proxy methods
originalArray.push('test2');
// the will however contain the same data,
// as the items get added to the referenced array
console.log('Both proxy and original array have the same content? '
+ (proxyToArray.join(',') === originalArray.join(',')));
// expect false here, as strict equality is incorrect
console.log('They strict equal to eachother? ' + (proxyToArray === originalArray));
然后输出:
getting push for
getting length for
setting 0 for with value Test
setting length for Test with value 1
getting 0 for Test
Test
代理的警告是,在对象上定义的所有内容都将被拦截,这可以在使用
push
时观察到。方法。将被代理的原始对象不会发生变化,并且对原始对象所做的更改不会被代理捕获。
关于javascript - 使用 Proxy 对象检测 Javascript 数组中的更改,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35610242/