“|”的功能是什么？ （管道）操作员？ [英] What's the function of the "|" (pipe) operator?

问题描述

我从另一个地方复制了这一行：

I have this line that I copied from another place:

Total += parseFloat($(this).val())|0;

运营商的功能是什么 | ？当我更改数字时，我会得到不同的结果。

What's the function of the operator |? When I change the number, I get different results.

推荐答案

| 在JavaScript中是整数按位OR运算符。在这种情况下，它会剥离 parseFloat 返回的任何小数部分。表达式 parseFloat（$（this）.val（））将导致一个带有（可能）小数组件的数字，但是 | 0 将将其转换为整数，或者 0 （这意味着它不会改变），因此总体结果是得到一个整数。

The | in JavaScript is an integer bitwise OR operator. In that context, it strips off any fractional portion returned by parseFloat. The expression parseFloat($(this).val()) will result in a number with (potentially) a fractional component, but then |0 will convert it to an integer number, OR it with 0 (which means it won't change), and so the overall result is to get a whole number.

所以功能上如此，它截断数字的小数部分。 -1.5 变为 -1 ， 1.5 变为 1 。这就像 Math.floor ，但截断而不是舍入向下（ Math.floor（-1.5）是 -2  —下一个最低整数 —而不是 -1 因为 | 0 版本给了我们。）

So functionally, it truncates the fractional portion off the number. -1.5 becomes -1, and 1.5 becomes 1. This is like Math.floor, but truncating rather than rounding "down" (Math.floor(-1.5) is -2 — the next lowest whole number — rather than -1 as the |0 version gives us).

所以也许这就是为什么它被用来切断（而不是地板）数字的小数部分。

So perhaps that's why it was used, to chop off (rather than "floor") the fractional portion of the number.

或者，它可能是一个错字。该代码的作者可能打算写这个（注意 || 而不是 | ）：

Alternately, it could be a typo. The author of that code might have meant to write this (note || rather than |):

Total += parseFloat($(this).val()) || 0;

这可以防止 $（this）.val（）返回或类似内容，导致 parseFloat 返回 NaN 。它使用奇怪的强大 || 运算符在这种情况下返回 0 而不是 NaN 。 （并且有一个广告，用于在您的运营商周围放置空格。）必须知道代码的上下文，以说明是否截断为整数（ | ）在添加到 Total 时有意义，或者他们只是在捍卫 NaN 案例。

That defends against the possibility that $(this).val() returns "" or similar, resulting in parseFloat returning NaN. It uses the curiously-powerful || operator to return 0 rather than NaN in that case. (And there's an advertisement for putting spaces around your operators.) Would have to know the context of the code to say whether truncating to a whole number (|) makes sense when adding to Total, or if they were just defending the NaN case.

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