为什么JQuery和Javascript DOM方法去除空格？

Question

I'm trying to write a chatroom in Javascript. It seems as if you send hello in the message submission box, it places hello in the message log on everybody's message log. I have also tried to use the native DOM methods, and the same thing happens there too.

The Javascript to place the message in the log is like this:

socket.on('chat message', function(msg){
        $('#messages').append($('<li style="background: #ffffff;">' + msg + '</li>'))
})

The HTML of where it would be placed is like this:

<ul id="messages">
</ul>

Can somebody please tell me why this happens, and how I could keep this from happening.

Answer 1

Browsers don't always display breaking whitespace when showing text, you can change that with CSS

#messages li {
  white-space: pre;
}

The valid values are as follows

Value    |  Description
_________|_________________________________________________________________________
normal   |  Sequences of whitespace will collapse into a single whitespace. 
         |  Text will wrap when necessary. This is default.
_________|_________________________________________________________________________
nowrap   |  Sequences of whitespace will collapse into a single whitespace. 
         |  Text will never wrap to the next line. 
         |  The text continues on the same line until a <br> tag is encountered.
_________|_________________________________________________________________________
pre      |  Whitespace is preserved by the browser. 
         |  Text will only wrap on line breaks.  
         |  Acts like the <pre> tag in HTML.
_________|_________________________________________________________________________
pre-line |  Sequences of whitespace will collapse into a single whitespace.
         |  Text will wrap when necessary, and on line breaks.
_________|_________________________________________________________________________
pre-wrap |  Whitespace is preserved by the browser. 
         |  Text will wrap when necessary, and on line breaks.
_________|_________________________________________________________________________
initial  |  Sets this property to its default value.
_________|_________________________________________________________________________
inherit  |  Inherits this property from its parent element.
_________|_________________________________________________________________________

 var msg = "hello"; $('#messages').append($('<li style="background: #ffffff;">' + msg + '</li>')); $('#messages2').append($('<li style="background: #ffffff;">' + msg + '</li>')); 

 #messages li { white-space: pre } 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <ul id="messages"><li>With white-space</li></ul> <ul id="messages2"><li>Without white-space</li></ul> 

Answer 2

您应该将msg附加到pre标签，这将阻止浏览器格式化文本：

$('#messages').append($('<li style="background: #ffffff;"><pre>' + msg + '</pre></li>'))