[英]How to listen for a variable change in Javascript?
我一直在使用Node.js和CouchDB。 我想要做的是在对象中进行db调用。 这是我现在正在看的场景:
var foo = new function(){
this.bar = null;
var bar;
calltoDb( ... , function(){
// what i want to do:
// this.bar = dbResponse.bar;
bar = dbResponse.bar;
});
this.bar = bar;
}
所有这一切的问题是CouchDB回调是异步的,“this.bar”现在在回调函数的范围内,而不是类。 有没有人有任何想法来完成我想要的东西? 我不希望有一个处理程序对象必须对对象进行db调用,但是现在我真的很难理解它是异步的。
请保持this
的参考:
function Foo() {
var that = this; // get a reference to the current 'this'
this.bar = null;
calltoDb( ... , function(){
that.bar = dbResponse.bar;
// closure ftw, 'that' still points to the old 'this'
// even though the function gets called in a different context than 'Foo'
// 'that' is still in the scope and can therefore be used
});
};
// this is the correct way to use the new keyword
var myFoo = new Foo(); // create a new instance of 'Foo' and bind it to 'myFoo'
保存this
的引用,如下所示:
var foo = this;
calltoDb( ... , function(){
// what i want to do:
// this.bar = dbResponse.bar;
foo.bar = dbResponse.bar;
});
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.