监听 Javascript 对象值的变化
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Listen for change to Javascript object value
提问by redhotvengeance
Is it possible (using jQuery or otherwise) to listen for a change in the value of a non-DOM Javascript object (or variable)? So, for instance, I have:
是否有可能（使用 jQuery 或其他方式）监听非 DOM Javascript 对象（或变量）的值的变化？因此，例如，我有：
function MyObject()
{
this.myVar = 0;
}
var myObject = new MyObject();
myObject.myVar = 100;
Is there a way to listen for when the value of myVarchanges and call a function? I know that I could use getter/setters, but they aren't supported in previous versions of IE.
有没有办法侦听值何时myVar发生变化并调用函数？我知道我可以使用 getter/setter，但它们在以前版本的 IE 中不受支持。
采纳答案by mplungjan
If IE is important, I guess you are not interested in Watch
如果 IE 很重要，我猜你对Watch不感兴趣
But someone seems to have written a shim which makes this question a duplicate
但似乎有人写了一个垫片，使这个问题重复
回答by Andris
Basically you have two options
基本上你有两个选择
- use non-standard
watchmethod which is available only in Firefox - use getters and setters which are not supported in older IE versions
- 使用
watch仅在 Firefox 中可用的非标准方法 - 使用旧版 IE 不支持的 getter 和 setter
The third and cross-platform option is to use polling which is not so great
第三个跨平台选项是使用轮询，这不是很好
Example of watch
示例 watch
var myObject = new MyObject();
// Works only in Firefox
// Define *watch* for the property
myObject.watch("myVar", function(id, oldval, newval){
alert("New value: "+newval);
});
myObject.myVar = 100; // should call the alert from *watch*
Example of gettersand setters
getters和的例子setters
function MyObject(){
// use cache variable for the actual value
this._myVar = undefined;
}
// define setter and getter methods for the property name
Object.defineProperty(MyObject.prototype, "myVar",{
set: function(val){
// save the value to the cache variable
this._myVar = val;
// run_listener_function_here()
alert("New value: " + val);
},
get: function(){
// return value from the cache variable
return this._myVar;
}
});
var m = new MyObject();
m.myVar = 123; // should call the alert from *setter*
回答by Alexander Beletsky
You can basically implement such behavior
你基本上可以实现这样的行为
function MyObject(onMyVarChangedCallback)
{
this.myVar = 0;
this.setMyVar = function (val) {
this.MyVar = val;
if (onMyVarChangedCallback) {
onMyVarChangedCallback();
}
}
}
function onChangeListener() {
alert('changed');
}
var o = new MyObject(onChangeListener);
