Multiline strings in JavaScript

That's a really smart hack, I didn't realize comments were included in the output of Function#toString. You could do other cool things, e.g. an annotation for type checking:

  function checkType(f) {
    return function(a) {
      var type = f.toString().match(/\/\/(.*)\n/)[1].trim();
      if(type !== typeof(a)) throw new Error('Invalid type');
      return f(a);
    }
  }
  
  var halve = checkType(function(n) {
    // number
    return n / 2;
  });
  
  halve(4); // returns 2
  halve('string'); // emits error

When I was first really to program I was into hacking javascript to do the crazy things I wanted it to do. I basically did exactly this, albeit with a worse interpolation feature[1]. Don't actually do this please. In the browser, just open up a different <script type="text/plain"> and grab the string from that tag. On the server you can just use a file. Any string that's actually long enough for `["foo", "bar"].join("\n")` to be too cumbersome should be in a separate file, especially if the other way involves a massive hack.

[1]: http://zurb.com/forrst/posts/Javascript_native_multi_line_st...

Probably worth pointing out that this won't play nice with most minification utilities unless you don't mind leaving all comments in the output.

I think for this reason I still prefer using Array.prototype.join for multiline strings:

    var str = [
        '<!doctype html>',
        '<html>',
            '<body>',
                '<h1>❤ unicorns</h1>',
            '</body>',
        '</html>',
    ].join('');

Yep, I could use this: http://i.gyazo.com/7826deb9e267f52e1f6b4f1afcfb8c4e.png

Interesting solution. I usually find this type of problem when doing templating in the client when updating things via Ajax. I either use the DOM to store the template or end up concatenating for smaller things.

Since to preserve these comments in minification requires conscious effort, I wonder if there's an alternative that could convert the comments to regular JS before minification. Obviously you can't just run it in Node as normal doing it this way.

FYI, CoffeeScript has multiline strings (and a bunch of other nice things!)

I thank you from the bottom of my heart. This drove me crazy when playing around with WebGL and shaders, because for various reasons I didn't want to put those in separate files.

The first problem I see, is using any build process which will remove all the comments. Therefore your string will become ''. I wonder how to avoid this.

>Note that ES6 will have template string which can be multiline, but time...

Firefox Nightly currently supports just enough of template strings to give you multiline strings.

Cool hack, but a cleaner solution would be to just use fs.readFileSync if you really want long strings, and let browserify/brfs to inline it for you in the browser.

Using this in a library would be pretty unsafe, given how it's browser-dependent, is prone to issues with minifcation, and could just break with future versions of your JS engine.

seriously? you people be nuts

    http://stackoverflow.com/a/15558082/2371924
    var myString = function(){/*
      multi-line
      string
    */}.toString().slice(14,-3)

take this code snippet, throw a package.json and some yaml in and make another npm to Show HN.

At one point the E4X standard (back in 2007?) enabled a cool multi-line string hack by promoting XML elements to language entities. You could say:

    var htmlFragment = "" + (<r><![CDATA[
    l(a
    
    le
    af
    fa
    
    ll
    
    s)
    one
    l
    
    iness
    
    - e.e. cummings
    ;
    ]]></r>);

And then `htmlFragment` would contain your multi-line string. (The addition with the empty string coerces the <r> element to output its `toString()` value, which happens to be the innerHTML).

This is largely a historical factoid, though. I don't think browsers beyond Mozilla ended up supporting E4X.

Really clever hack with the function's toString method!

Cool hack but not supporting multiline strings is a feature as far as I'm concerned. Everyone seems to agree that HTML shouldn't contain JavaScript, why should JavaScript contain HTML?

This snippet does the same thing, mostly:

    var multiline = function(){/*
    foo
    bar
    baz
    */}.toSource().match(/\/\*([\s\S]*)\*\//)[1].trim()

I just use ES6 template strings together with the es6ify transform for Browserify. Works in all browsers and very likely performs much better than using Function.prototype.toString.

If you do multi line strings you could probably do it in a smarter way. Examples:

appendChild instead of innerHTML .html file instead of html inside a .js file. .css file instead of css inside a .js file.

It can get very messy if you store "data" inside JS. Especially if you store markup or styling in the JS.

Wouldn't something like a Sweet.js macro be better for this? Just have it output a string with '\n\' at the end of lines, or using Array.join() or whatever you like.

This is really handy for DFP creative templates. Thank you.

Today I learned that in JavaScript, comments are significant and part of the code.

(And people complain about Python having significant whitespace?)

Weird... I just just randomly looking at this a few days ago upon a search for "js multiline" when wondering about the common way to spell multiline (multi line vs multi-line vs multiline). I was intrigued by his code though, ultimately in awe of the cleverness and conciseness of it. Very cool hack! Crazy coincidence to see the very code on HN only a few days later.

Be sure to scroll to the bottom for a real-world example, this is very brittle.

In other news, the ubiquitous language of the ubiquitous platform of the information age doesn't support multiline strings. But I guess if we keep throwing enough modules and libraries at it, it'll end up being nice to develop for.

Alternatively wait for ES6 or ES7 to (maybe) solve the problem.

This is a very clever hack. Great use of anonymous functions and toString.

Why not a pre-processor?

I think i saw 8 libraries before who abused comments like this.

Edit: Yawn.