the pattern text = <<"HERE" This Is A Multiline String HERE is not available in js (I remember using it much in my good old Perl days).

To keep oversight with complex or long multiline strings I sometimes use an array pattern:

var myString = 
   ['<div id="someId">',
    'some content<br />',
    '<a href="#someRef">someRefTxt</a>',
    '</div>'
   ].join('\n');

or the pattern anonymous already showed (escape newline), which can be an ugly block in your code:

    var myString = 
       '<div id="someId"> \
some content<br /> \
<a href="#someRef">someRefTxt</a> \
</div>';

Google's javascript style guide recommends to use string concatenation instead of escaping newlines because the latter isn't a part of ECMAscript:

http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml?showone=Multiline_string_literals#Multiline_string_literals

Update

var htmlString = `Say hello to 
multi-line
strings!`;

I think you can try this and other features by first downloading canary chrome and then turning on Enable Experimental JavaScript

You can have multiline strings in pure JavaScript.

This method is based on the serialization of functions, which is defined to be implementation-dependent. It does work in the most browsers (see below), but there's no guarantee that it will still work in the future, so do not rely on it.

Using the following function:

function hereDoc(f) {
  return f.toString().
      replace(/^[^\/]+\/\*!?/, '').
      replace(/\*\/[^\/]+$/, '');
}

You can have here-documents like this:

var tennysonQuote = hereDoc(function() {/*!
  Theirs not to make reply,
  Theirs not to reason why,
  Theirs but to do and die
*/});

The method has successfully been tested in the following browsers (not mentioned = not tested):

• IE 4 - 10
• Opera 9.50 - 12 (not in 9-)
• Safari 4 - 6 (not in 3-)
• Chrome 1 - 27
• Firefox 17 - 21 (not in 16-)
• Rekonq 0.7.0 - 0.8.0
• Not supported in Konqueror 4.7.4

Be careful with your minifier, though. It tends to remove comments. For the YUI compressor, a comment starting with /*! (like the one I used) will be preserved.

I think a real solution would be to use CoffeeScript.

You can do this...

var string = 'This is ' +
'multiline' + 
'string';

I'm surprised I didn't see this, because it works everywhere I've tested it and is very useful for e.g. templates:

<script type="bogus" id="multi">
    My
    multiline
    string
</script>
<script>
    alert($('#multi').html());
</script>

Does anybody know of an environment where there is HTML but it doesn't work?

I came up with this very jimmy rigged method of a multi lined string. Since converting a function into a string also returns any comments inside the function you can use the comments as your string using a multilined comment /**/. You just have to trim off the ends and you have your string.

var myString = function(){/*
    This is some
    awesome multi-lined
    string using a comment 
    inside a function 
    returned as a string.
    Enjoy the jimmy rigged code.
*/}.toString().slice(14,-3)

alert(myString)

I solved this by outputting a div, making it hidden, and calling the div id by jQuery when i needed it.

e.g.

<div id="UniqueID" style="display:none;">
     Strings
     On
     Multiple
     Lines
     Here
</div>

Then when i need to get the string, i just use the following jQuery:

$('#UniqueID').html();

Which returns my text on multiple lines. If i call

alert($('#UniqueID').html();

I get:

I like this syntax and indendation:

string = 'my long string...\n'
       + 'continue here\n'
       + 'and here.';

(but actually can't be considered as multiline string)

Using script tags:

• add a <script>...</script> block containing your multiline text into head tag;

• get your multiline text as is... (watch out for text encoding: UTF-8, ASCII)

  <script>
  
      // pure javascript
      var text = document.getElementById("mySoapMessage").innerHTML ;
  
      //jQuery... using document ready for safety
      $(document).ready(function() {
  
          var text = $("#mySoapMessage").html(); 
  
      }
  
  </script>
  
  <script id="mySoapMessage">
  
      <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:typ="...">
         <soapenv:Header/>
         <soapenv:Body>
            <typ:getConvocadosElement>
               ...
            </typ:getConvocadosElement>
         </soapenv:Body>
      </soapenv:Envelope>
  
      <!-- this comment will be present on your string -->
      //uh-oh, javascript comments...  SOAP request will fail 
  
  
  </script>
  

to sum up, I have tried 2 approaches listed here in user javascript programming (Opera 11.01):

• this one didn't work: Multiline strings in Javascript
• this worked fairly well, I have also figured out how to make it look good in Notepad++ source view: Multiline strings in Javascript

So I recommend the working approach for Opera user JS users. Unlike what the author was saying:

It doesn't work on firefox or opera; only on IE, chrome and safari.

It DOES work in Opera 11. At least in user JS scripts. Too bad I can't comment on individual answers or upvote the answer, I'd do it immediately. If possible, someone with higher privileges please do it for me.

Just tried the Anonymous answer and found there's a little trick here, it doesn't work if there's a space after backslash \
So the following solution doesn't work -

var x = { test:'<?xml version="1.0"?>\ <-- One space here
            <?mso-application progid="Excel.Sheet"?>' 
};

But when space is removed it works -

var x = { test:'<?xml version="1.0"?>\<-- No space here now
          <?mso-application progid="Excel.Sheet"?>' 
};

alert(x.test);​

Hope it helps !!

I think this workaround should work in IE, Chrome, Firefox, Safari, Opera -

Using jQuery :

<xmp id="unique_id" style="display:none;">
  Some plain text
  Both type of quotes :  " ' " And  ' " '
  JS Code : alert("Hello World");
  HTML Code : <div class="some_class"></div>
</xmp>
<script>
   alert($('#unique_id').html());
</script>

Using Pure Javascript :

<xmp id="unique_id" style="display:none;">
  Some plain text
  Both type of quotes :  " ' " And  ' " '
  JS Code : alert("Hello World");
  HTML Code : <div class="some_class"></div>
</xmp>
<script>
   alert(document.getElementById('unique_id').innerHTML);
</script>

Cheers!!

I think I discovered another way to do it inline without any invasive syntax on every line. Use Javascript's ability to convert a function to string and create a multiline comment with the /**/ syntax then remove the "function() {/*\n" and "\n*/}".

var multiline = function(string) { return string.toString().replace(/(^[^\n]*\n)|(\n\*\/\})/g, ""); };

console.log(multiline(function() {/*
Hello world!
I'm a multiline string!

Tada!
*/}));

The only pitfall I can see in this is the syntax highlighting.

EDIT: Had I scrolled down a little more, I would have seen this answer doing exactly the same thing: http://stackoverflow.com/a/5571069/916553

My version of array-based join for string concat:

var c = []; //c stands for content
c.push("<div id='thisDiv' style='left:10px'></div>");
c.push("<div onclick='showDo(\'something\');'></div>");
$(body).append(c.join('\n'));

This has worked well for me, especially as I often insert values into the html constructed this way. But it has lots of limitations. Indentation would be nice. Not having to deal with nested quotation marks would be really nice, and just the bulkyness of it bothers me.

Is the .push() to add to the array taking up a lot of time? See this related answer:

(Is there a reason JavaScript developers don't use Array.push()?)

After looking at these (opposing) test runs, it looks like .push() is fine for string arrays which will not likely grow over 100 items - I will avoid it in favor of indexed adds for larger arrays.

This works in IE, Safari, Chrome and Firefox:

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"></script>
<div class="crazy_idea" thorn_in_my_side='<table  border="0">
                        <tr>
                            <td ><span class="mlayouttablecellsdynamic">PACKAGE price $65.00</span></td>
                        </tr>
                    </table>'></div>
<script type="text/javascript">
    alert($(".crazy_idea").attr("thorn_in_my_side"));
</script>

This works at least in Firefox:

var text = <>
some
multiline
text
</>.toString();

This seems to work in Fx 19 and Chrome 24 on Mac

DEMO

var new_comment; /*<<<EOF 
    <li class="photobooth-comment">
       <span class="username">
          <a href="#">You</a>
       </span>
       <span class="comment-text">
          $text
       </span>
       <span class="comment-time">
          2d
       </span>
    </li>
EOF*/
// note the script tag here is hardcoded as the FIRST tag 
new_comment=document.getElementsByTagName('script')[0].innerHTML.split("EOF")[1]; 
alert(new_comment.replace('$text','Here goes some text'));

This is one fairly economical approach, at least in terms of the source code:

function s() {
    var args = [];
    for (var index = 0; index< arguments.length; index++) {
        args.push (arguments [index]);
    }
    return args.join ("\n");
}
console.log (s (
    "This is the first line",
    "and this is the second",
    "finally a third"
));

function s() {return.arguments.join ("\n")} 

would be nicer of course if the "arguments" property were a proper array.

A second version might use "" to do the join for cases when you want to control the line breaks in a very long string.

I program this way:

sys = {
    layout: null,
    makeLayout: function (obCLS) {
        this.layout = $('<div />').addClass('editor').appendTo($(obCLS)).append(

            /* Cargador */
            /* @this.layout.find('> div:nth-of-child(1)'); */
            '<div>' +
            '   <p>Seleccione la imagen que desea procesar.</p>' +
            '   <input type="button" value="Seleccionar" class="btn btn-xlarge btn-success" />' +
            '   <span></span>' +
            '</div>' +

            /* Cargador - Progreso */
            /* @this.layout.find('> div:nth-of-child(2)'); */
            '<div>' +
            '   <div>' +
            '       <div></div>' +
            '       <div>' +
            '           <div></div>' +
            '       </div>' +
            '   </div>' +
            '</div>' +

            /* Editor */
            /* @this.layout.find('> div:nth-of-child(3)');
             * @sidebar = this.layout.find('> div:nth-of-child(3) > div > div > div:nth-of-type(1)');
             * @body    = this.layout.find('> div:nth-of-child(3) > div > div > div:nth-of-type(2) > div'); */
            '<div>' +
            '   <div>' +
            '       <div>' +
            '           <div></div>' +
            '           <div>' +
            '               <div></div>' +
            '           </div>' +
            '       </div>' +
            '   </div>' +
            '</div>'
        );
    }
}

sys.makeLayout('#div');

check this,

Multi-Line JavaScript Strings

See also this performance test from different possibilities; the \ variant is the fastest.

performance test