textarea 值是否为空 - 检查 jquery 不起作用，为什么
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textarea value is empty or not - check with jquery not working, why
提问by doniyor
i have this code, commentis id of textarea:
我有这个代码，comment是 id textarea：
<textarea id="comment"> </textarea>
js
js
var comment = $('#comment').val();
if(comment.length === 0){
alert('empty');
return;
}else{
alert('not empty');
}
it is giving me not empty even if it is empty. why is this? i cannot check like !=""because whitespace will pass the check and i would have to check for all whitespaces then
即使它是空的，它也给我不空。为什么是这样？我无法检查，!=""因为空格会通过检查，然后我必须检查所有空格
please help
请帮忙
回答by PSL
Remove space in your textarea or trim the value
删除文本区域中的空间或修剪值
<textarea id="comment"></textarea>
or
或者
var comment = $.trim($('#comment').val());
Also btw if you are returning after ifyou dont need an else
顺便说一句，如果您在if不需要后返回else
var comment = $.trim($('#comment').val());
if(comment.length == 0){
alert('empty');
return;}
alert('not empty');
回答by Niccolò Campolungo
I bet it does the opposite of what you expect, right?
我敢打赌它与您期望的相反，对吗？
I think you need to study how it works, even if it is a logical problem. If the length of the string is 0 it is empty, otherwise it is not.
我认为你需要研究它是如何工作的，即使它是一个逻辑问题。如果字符串的长度为 0，则为空，否则为空。
var comment = $.trim($('#comment').val());
if(comment.length === 0){
alert('empty');
return;
}
alert('not empty');
回答by techfoobar
Should work if you trim()the value before checking its length.
如果您trim()在检查其长度之前使用该值，则应该可以工作。
var comment = $.trim($('#comment').val());
if(comment.length !== 0) {
...
回答by Arun
You need to trim the value before checking and it can be done in one line
您需要在检查之前修剪该值，并且可以在一行中完成
alert($.trim($('#comment').val()) == "" ? "Empty" : "Not Empty");
