Javascript“这个”范围
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Javascript "this" scope
提问by bluetech
I am writing some JavaScript code. I am a little confused about this keyword. How do I access logger variable in the dataReceivedHandlerfunction?
我正在编写一些 JavaScript 代码。我对这个关键字有点困惑。如何访问dataReceivedHandler函数中的记录器变量？
MyClass: {
logger: null,
init: function() {
logger = LogFactory.getLogger();
},
loadData: function() {
var dataReceivedHandler = function() {
// how to access the logger variable here?
}
// more stuff
}
};
回答by doowb
You can do something like this inside the loadData function to access your object...
你可以在 loadData 函数中做这样的事情来访问你的对象......
MyClass: {
logger: null,
init: function() {
this.logger = LogFactory.getLogger();
},
loadData: function() {
var self = this;
var dataReceivedHandler = function() {
// how to access the logger variable here?
self.logger.log('something');
}
// more stuff
}
};
回答by Matt Ball
Assuming loadDatais called like so:
假设loadData是这样调用的：
MyClass.loadData();
then:
然后：
loadData: function() {
var self = this;
var dataReceivedHandler = function() {
self.logger ...
}
// more stuff
}
回答by iMoses
Because dataReceivedHandleris an anonymous function thiswill refer to the window object on the global scope. I think of two way you can bypass that.
因为dataReceivedHandler匿名函数this会在全局范围内引用 window 对象。我想到了两种方法可以绕过它。
a) Create a variable inside loadDatato hold it's context then use it inside dataReceivedHandleras such:
a) 在里面创建一个变量loadData来保存它的上下文，然后在里面使用它dataReceivedHandler：
loadData: function() {
var self = this;
var dataReceivedHandler = function() {
console.log(self.logger);
}
// more stuff
}
b) Change the context of your anonymous function using applyor call.
loadData: function() {
var dataReceivedHandler = function() {
console.log(this.logger);
}
// more stuff
dataReceivedHandler.call(this); // by passing this as the first argument we make sure the context of the excuted function is our current scope's this
}
I prefer option B due to performance and memory usage optimizations, but both would work just fine.
由于性能和内存使用优化，我更喜欢选项 B，但两者都可以正常工作。
