为什么 ('b'+'a'+ + 'a' + 'a').toLowerCase() 'banana' 的结果是?
当我的一个朋友偶然发现这段 JavaScript 代码时，我正在练习一些 JavaScript:
I was practicing some JavaScript when one of my friends came across this JavaScript code:
document.write(('b' + 'a' + + 'a' + 'a').toLowerCase());以上代码回答"banana"！谁能解释一下为什么?
The above code answers "banana"!
Can anyone explain why?
推荐答案
+'a' 解析为 NaN ("Not a Number") 因为它强制转换为字符串为数字，而字符 a 不能被解析为数字.
+'a' resolves to NaN ("Not a Number") because it coerces a string to a number, while the character a cannot be parsed as a number.
document.write(+'a');小写变成banana.
"ba"加上NaN，由于类型转换，将NaN变成字符串"NaN"，给出 baNaN.然后后面有一个a，给出baNaNa.
Adding NaN to "ba" turns NaN into the string "NaN" due to type conversion, gives baNaN.
And then there is an a behind, giving baNaNa.
+ + 之间的空格是为了使第一个字符串连接和第二个一元加号(即正")运算符.如果你使用 'ba'+(+'a')+'a' 得到相同的结果，解析为 'ba'+NaN+'a'，即由于类型杂耍，相当于 'ba'+'NaN'+'a'.
The space between + + is to make the first one string concatenation and the second one a unary plus (i.e. "positive") operator.
You have the same result if you use 'ba'+(+'a')+'a', resolved as 'ba'+NaN+'a', which is equivalent to 'ba'+'NaN'+'a' due to type juggling.
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