ios9 Safari错误计算总和 [英] ios9 Safari miscalculating sum

问题描述

我有一些代码可以计算循环中哈希中键/值的总和。它似乎是在ios9 Safari上以不同的方式计算总和，与其他任何地方相比。虽然我可以找到一种方法来修复这个单独的用例，但是我们在整个大型代码库中都使用了这种类型的语法，所以我正在寻找一些理解

I have some code that calculates the sum of key/values in a hash in a loop. It appears to be calculating the sum in a different manner on ios9 Safari compared with anywhere else. Although I can find a way to fix this individual use case, we use this type of syntax throughout our large code base, so I am looking for some understanding of

1. 为什么在ios9中发生这种情况


2. 如果有办法全局修复它，那将适用于可能有Vue __ ob__的所有对象对象就可以了。

1. why this is happening in ios9
2. if there is a way to globally fix it that would be applicable to all objects that might have a Vue __ob__ object on them.

在此尝试代码： https://liveweave.com/kKo88G 。我还粘贴在下面：

Try the code out here: https://liveweave.com/kKo88G. I also pasted it below:

// Define a hash
var totalItems, sum, type, value
totalItems = {}
totalItems['0'] = 3

// This definition of __ob__ is done dynamically by Vue,
// but I include it here by way of example of what breaks in ios9
totalItems.__ob__ = new Object()
Object.defineProperty(totalItems, '__ob__', {
    enumerable: false,
    writable: true,
   configurable: true
  });

// Loop through the hash
sum = 0
for (type in totalItems) {
  value = totalItems[type];
  sum += value;
}

// sum is 6 in ios9 Safari -- it loops through the '0' key twice 
// sum is 3 in all other browsers and newer ios versions!

更新：

在进一步调查之后，这似乎是ios9设备上的Safari中的一个错误。它既适用于带有键'0'的哈希值，也适用于数组。这似乎只是 for-in 循环的问题。 .forEach ， .reduce 等工作正常。 https://liveweave.com/znUFU2 展示了这一点。如果liveweave首先加载缓慢，则刷新页面几次。 js fiddle / codepen / etc.目前不适用于ios9。我已向Apple报告此事。

After investigating further, this appears to be a bug in Safari on ios9 devices. It applies both to hashes with the key '0' in them and to arrays. It only seems to be an issue with for-in loops. .forEach, .reduce, etc. work fine. https://liveweave.com/znUFU2 showcases this. Refresh the page a couple of times if liveweave is slow to load at first. js fiddle/codepen/etc. don't work on ios9 at the moment. I have reported this to Apple.

推荐答案

通常使用 for ... in 并不是一件好事理念。我相信你的问题与此有关。

Usually using for ... in is not a good idea. I believe your issue is related to that.

您可以使用表示**或**进行常规** 循环。

在此处<查看有关...的详细说明/ a>

See a detailed explanation of what happens with for ... in here

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