numpy数组与布尔数组

One of the annoyances of old-school JavaScript was side effects; then Array.prototype got methods like filter, map, and forEach so we didn't need to burn variables before looping over values.  I can't explain how happy I am that the JavaScript language continues to evolve.

老式JavaScript的烦恼之一是副作用。 然后Array.prototype获得了filter ， map和forEach类的方法，因此我们不需要在遍历值之前刻录变量。 我无法解释JavaScript语言的不断发展让我多么高兴。

Every once in a while I need to filter an array by not its original value but instead a new value, so I use map:

每过一段时间，我需要进行过滤而不是它的原始值的阵列，而是一个新的价值，所以我使用map ：

myArray.map(item => {    // Do whatever processing...    // If we don't care about the item, return false or null or undefined    return false;});

While I get the new values I want, sometimes if an iteration returns a result I don't want, I return null or false, which is great, but then I'm left with a bunch of useless items in the resulting array.  The next step is using filter, in which case I could do:

当我获得所需的新值时，有时如果迭代返回了我不想要的结果，我将返回null或false，这很好，但是随后在结果数组中留下了一堆无用的项。 下一步是使用过滤器，在这种情况下，我可以这样做：

myArray    .map(item => {        // ...    })    // Get rid of bad values    .filter(item => item);

Since the values I don't want aren't truthy, the filter above removes those bad items.  Did you know there's a clearer way with Boolean?

由于我不想要的值不真实，因此上面的过滤器删除了这些不良项。 您是否知道Boolean有更清晰的方法？

myArray    .map(item => {        // ...    })    // Get rid of bad values    .filter(Boolean);

If the value isn't truthy the item is filtered out and I'm left with only the items I want!

如果值不正确，该项目将被过滤掉，而我只剩下我想要的项目！

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numpy数组与布尔数组