遍历在Javascript对象 [英] Iterating over objects in Javascript

问题描述

我有形式的obejct：

I have an obejct of the form:

var test = {"2011":{"10":4,"9":9,"8":15,"7":11,"6":11,"5":13,"4":9,"3":5,"2":9,"1":4,"0":20},"2010":{"11":9,"10":23,"9":58}}

我要遍历这个，所以我可以打每一个年份和月份组合。我有：

I want to iterate over this so I can hit each year and month combo. I have:

var years = d3.keys(test),
    months = d3.range(12),
    data = [];

所以，作为一个JavaScript新手，要完整性检查的事情，我检查年。

document.writeln(years)
2011,2010 

酷，但是当我尝试遍历年阵列获取数据了测试元素的我做我认为是正确的测试，但内容会丢失：

Cool, but when I try to iterate over the years array to pull data out of test the elements I do what I think is correct to test, but the elements are lost:

for(var y in years) {
  document.writeln(y);
}
0,1

我如何遍历年来得到实际的元素（ 2011,2010 ）在其中？

How do I iterate over years to get the actual elements (2011,2010) in them?

推荐答案

在检索索引/键（不是值）。

for in retrieves indices/keys (not the values).

您将需要修改你的循环，像这样：

You'll need to modify your loop, like so:

for(var y in years) {
  document.writeln(years[y]);
}

修改 - 每missingno的评论，使用迭代数组在是的坏主意。

EDIT - per missingno's comment, iterating over an array using for in is a bad idea.

for(var i = 0, l = years.length; i < l; i++) {
  document.writeln(years[i]);
}

一点点额外的信息......如果您使用了/在打击的对象循环同样会遍历你的属性键。例如，

A little extra information... if you use a for/in loop against an object it will also iterate over your property keys. For example,

for(var y in test) {
  //This will yield, "2011" and then "2010"
  document.writeln(y);
}

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