防止连接 [英] Preventing concatenation

问题描述

我已经写了13年的JavaScript，但我在过去的几个月里重新发现了它作为一种编写程序的方式，任何访问网页的人都可以使用它而无需安装任何东西。请参阅示例。

I've been writing JavaScript on and off for 13 years, but I sort of rediscovered it in the past few months as a way of writing programs that can be used by anyone visiting a web page without installing anything. See for example.

我最近发现的showstopper是因为JavaScript在设计上是松散类型的，所以当我希望它添加数字时，它会保持连接字符串。这是不可预测的。一个例程工作好几天，然后当我输入不同的数据时问题就出现了，我最终得到了一个不可思议的大数字。

The showstopper I've recently discovered is that because JavaScript is loosely typed by design, it keeps concatenating strings when I want it to add numbers. And it's unpredictable. One routine worked fine for several days then when I fed different data into it the problem hit and I ended up with an impossibly big number.

有时候我运气不好这通过在一个术语周围加上（），有时候我不得不求助于 parseInt（）或<$ c一个学期的$ c> parseFloat（）。它提醒我一点点试图通过在一个（常量）项上放置.00来强制将结果放入C中。我只是通过 parseFloat（）尝试 + = 来自我已经加载的数组中的某些东西关于一切。

Sometimes I've had luck preventing this by putting ( ) around one term, sometimes I've had to resort to parseInt() or parseFloat() on one term. It reminds me a little of trying to force a float result in C by putting a .00 on one (constant) term. I just had it happen when trying to += something from an array that I was already loading by doing parseFloat() on everything.

这是否只会发生？如果我每次添加至少一个术语时使用 parseInt（）或 parseFloat（），那么防止它？我在Linux下使用Firefox 6进行编写，但浏览器的可移植性也是一个问题。

Does this only happen in addition? If I use parseInt() or parseFloat() on at least one of the terms each time I add, will that prevent it? I'm using Firefox 6 under Linux to write with, but portability across browsers is also a concern.

推荐答案

规范说明了加法运算符：

如果Type（ lprim ）是String或Type（ rprim ）是String，那么

返回String是连接ToString（ lprim ）后跟ToString（ rprim ）

If Type(lprim) is String or Type(rprim) is String, then
Return the String that is the result of concatenating ToString(lprim) followed by ToString(rprim)

<的结果p>这意味着如果至少有一个运算符是字符串，则会发生字符串连接。

Which means that if at least one operator is a string, string concatenation will take place.

如果我使用 parseInt（）或 parseFloat（）每次添加时至少有一个术语会阻止它吗？

If I use parseInt() or parseFloat() on at least one of the terms each time I add, will that prevent it?

不，所有操作数必须是数字。

No, all operands have to be numbers.

您可以轻松地将任何数字字符串转换为一个使用 一元加运算符（如果您已经处理过，它将不会更改该值数字）：

You can easily convert any numerical string into a number using the unary plus operator (it won't change the value if you are already dealing with a number):

var c = +a + +b;

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