I have encountered a similar problem described here (and in other places) - where as on an ajax callback I get a xmlhttp.responseText that seems ok (when I alert it - it shows the right text) - but when using an 'if' statement to compare it to the string - it returns false.(我在这里 （和其他地方）遇到了类似的问题-在ajax回调中，我得到一个看起来不错的xmlhttp.responseText（当我发出警报时-它显示正确的文本）-但是当使用'if'时将其与字符串进行比较的语句-返回false。)
(I am also the one who wrote the server-side code returning that string) - after much studying the string - I've discovered that the string had an "invisible character" as its first character.(（我也是编写返回该字符串的服务器端代码的人）-在研究了字符串之后-我发现该字符串的第一个字符为“不可见字符”。) A character that was not shown.(未显示的字符。) If I copied it to Notepad - then deleted the first character - it won't delete until pressing Delete again.(如果我将其复制到记事本中-然后删除了第一个字符-直到再次按Delete键，它才会删除。) I did a charCodeAt(0) for the returned string in xmlhttp.responseText.(我为xmlhttp.responseText中的返回字符串做了一个charCodeAt（0）。) And it returned 65279 .(然后返回65279 。) Googling it reveals that it is some sort of a UTF-8 control character that is supposed to set "big-endian" or "small-endian" encoding.(谷歌搜索它表明它是某种UTF-8控制字符，应该设置“大端”或“小端”编码。) So, now I know the cause of the problem - but... why does that character is being echoed?(所以，现在我知道了问题的原因-但是...为什么要回显该字符？) In the source php I simply use(在源PHP中，我只是使用)echo 'the string'...
and it apparently somehow outputs [chr(65279)]the string...(它显然以某种方式输出[chr（65279）]字符串...)
Why?(为什么？) And how can I avoid it?(我该如何避免呢？)
ask by Yuval A. translate from so
