为什么NaN(“"“)(带空格的字符串)等于false? [英] Why does isNaN(" ") (string with spaces) equal false?

问题描述

在JavaScript中，为什么isNaN(" ")评估为false，而isNaN(" x")评估为true?

In JavaScript, why does isNaN(" ") evaluate to false, but isNaN(" x") evaluate to true?

我正在对文本输入字段执行数字运算，并且正在检查该字段是null，""还是NaN.当有人在该字段中输入少量空格时，我的验证在这三个字段上都失败了，我困惑为什么它不能通过isNaN检查.

I’m performing numerical operations on a text input field, and I’m checking if the field is null, "", or NaN. When someone types a handful of spaces into the field, my validation fails on all three, and I’m confused as to why it gets past the isNaN check.

推荐答案

JavaScript将一个空字符串解释为0，然后失败了isNAN测试.您可以先在字符串上使用parseInt，该字符串不会将空字符串转换为0.然后结果应为NAN.

JavaScript interprets an empty string as a 0, which then fails the isNAN test. You can use parseInt on the string first which won't convert the empty string to 0. The result should then fail isNAN.

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