在for循环中关闭/回调 [英] Closure/callback in for loop

问题描述

可能重复：

Javascript循环中的事件处理程序 - 需要关闭吗？

我一直在努力让这个工作一段时间，并决定只问。

我有以下：

  function doSomething（var1，var2）{
 dojo.xhrGet（{
 url：somUrl，
 content：{value1：var1，value2：var2}，
 preventCache：true，
 handleAs：json，
 load：function（response）{
 for i in response.myObject）{
 var listItem = new dojox.mobile.ListItem（{
 label：response.myObject [i] .name，
 rightText：response.myObject [i]。 value，
 clickable：true，
 onClick：function（）{
 customFunction（response.myObject [i]）; 
 this.transitionTo（someScreen）; 
} 
}）; 
 myList.addChild（listItem）; 
} 
}，
 error：function（e）{alert（e）;} 
}）; 
} 
 doSomething（myVal1，myVal2）; 
 

customFunction（response.myObject [i]）; / code>总是返回myObject arrray中的最后一个对象。

有人可以帮助我的语法，所以我可以使这项工作正常吗？我已经阅读关于js关闭和回调，但我只是不能让它工作。

感谢

  onClick：（function（obj）{ 
 return function（）{
 customFunction（obj）; 
 this.transitionTo（someScreen）; 
}; 
}）（response.myObject [i] ）
  

查看此回答说明：

范围是函数级的，而不是块级的，创建
a闭包只是意味着封闭范围被添加到封闭函数的
词法环境中。

循环结束后，函数级变量 i 具有
值 5 注意：或 内部函数看到。

Possible Duplicate:
Event handlers inside a Javascript loop - need a closure?

I have been trying to get this to work for a while and decided to just ask.

I have the following:

function doSomething(var1, var2) {
    dojo.xhrGet({
        url:"somUrl",
        content: {value1:var1,value2:var2},
        preventCache: true,
        handleAs:"json",
        load: function(response){
            for(var i in response.myObject) {
                var listItem = new dojox.mobile.ListItem({
                    label: response.myObject[i].name,
                    rightText: response.myObject[i].value,
                    clickable: true, 
                    onClick: function() {
                        customFunction(response.myObject[i]);
                        this.transitionTo("someScreen");
                    }   
                });
                myList.addChild(listItem);
            }               
        },
        error:function(e){alert(e);}
    });
}
doSomething(myVal1, myVal2);

The line that says customFunction(response.myObject[i]); always returns the last object in the myObject arrray.

Can someone help me with the syntax so I can make this work correctly? I've been reading about js closures and callbacks but I just can't get it to work.

Thanks

解决方案

You need an additional wrapper function

onClick: (function(obj) {
    return function() {
        customFunction(obj);
        this.transitionTo("someScreen");
    };
})(response.myObject[i])

See this answer for an explanation:

JavaScript's scopes are function-level, not block-level, and creating a closure just means that the enclosing scope gets added to the lexical environment of the enclosed function.

After the loop terminates, the function-level variable i has the value 5 [note: or, in this case, the name of the last property in response.myObject], and that's what the inner function 'sees'.

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