将索引从 for 循环传递给 ajax 回调函数（JavaScript）
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passing index from for loop to ajax callback function (JavaScript)
提问by user717236
I have a for loop enclosing an ajax call and I'm trying to determine the best method for passing the index from the for loop to the callback function. Here is my code:
我有一个包含 ajax 调用的 for 循环，我正在尝试确定将索引从 for 循环传递到回调函数的最佳方法。这是我的代码：
var arr = [2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010];
for (var i = 0; i < arr.length; i++)
{
$.ajaxSetup({ cache:false })
$.getJSON("NatGeo.jsp", { ZipCode: arr[i], Radius:
document.getElementById("radius").value, sensor: false },
function(data)
{
DrawZip(data, arr[i]);
}
);
}
Currently, only the last value of the arr array is passed due to the asynchronous ajax call. How can I pass each iteration of the arr array to the callback function, aside from running the ajax call synchronously?
目前，由于异步 ajax 调用，仅传递 arr 数组的最后一个值。除了同步运行 ajax 调用之外，如何将 arr 数组的每次迭代传递给回调函数？
回答by scurker
You could use a javascript closure:
您可以使用 javascript 闭包：
for (var i = 0; i < arr.length; i++) {
(function(i) {
// do your stuff here
})(i);
}
Or you could just use $.each:
或者你可以只使用$.each：
var arr = [2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010];
$.each(arr, function(index, value) {
$.ajaxSetup({ cache:false });
$.getJSON("NatGeo.jsp", { ZipCode: value, Radius:
document.getElementById("radius").value, sensor: false },
function(data) {
DrawZip(data, value);
}
);
});
回答by yitwail
I didn't read all 30 questions @Anurag listed, but I found the following callback syntax that seems to work:
我没有阅读@Anurag 列出的所有 30 个问题，但我发现以下回调语法似乎有效：
(function(year) {
return (function(data) {DrawZip(data, year);});
})(arr[i])
This replaces the original function(data). Incidentally, the results are in random order, due to the asynchronous response
这取代了原来的function(data). 顺便说一下，由于异步响应，结果是随机的
回答by Herbi Shtini
You can even omit for-loop brackets as mentioned by John Resig herei think this way is more readable
您甚至可以省略John Resig 在这里提到的 for 循环括号，我认为这种方式更具可读性
for (var i = 0; i < arr.length; i++) (function(i) {
// async processing
setTimeout(function(){
console.log(i);
}, i * 200);
})(i);
