multiline

Multiline strings in JavaScript

multiline

Multiline strings in JavaScript

No more string concatenation or array join!

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

var str = '' +
'<!doctype html>' +
'<html>' +
'   <body>' +
'       <h1>❤ unicorns</h1>' +
'   </body>' +
'</html>' +
'';
var str = multiline(function(){/*
<!doctype html>
<html>
    <body>
        <h1>❤ unicorns</h1>
    </body>
</html>
*/});

It works by wrapping the text in a block comment, anonymous function, and a function call. The anonymous function is passed into the function call and the contents of the comment extracted.

Even though it's slower than string concat, that shouldn't realistically matter as you can still do 2 million of those a second. Convenience over micro performance always.

$ npm install --save multiline

Everything after the first newline and before the last will be returned as seen below:

var str = multiline(function(){/*
<!doctype html>
<html>
    <body>
        <h1>❤ unicorns</h1>
    </body>
</html>
*/});

Which outputs:

<!doctype html>
<html>
    <body>
        <h1>❤ unicorns</h1>
    </body>
</html>

You can use multiline.stripIndent() to be able to indent your multiline string without preserving the redundant leading whitespace.

    var str = multiline.stripIndent(function(){/*
            <!doctype html>
            <html>
                <body>
                    <h1>❤ unicorns</h1>
                </body>
            </html>
    */});

Which outputs:

<!doctype html>
<html>
    <body>
        <h1>❤ unicorns</h1>
    </body>
</html>

console.log() supports string substitution:

var str = 'unicorns';
 
console.log(multiline(function(){/*
  I love %s
*/}), str);
 
//=> I love unicorns 

Have one? Let me know.

I've also done an experiment where you don't need the anonymous function. It's too fragile and slow to be practical though.

It generates a callstack and extracts the contents of the comment in the function call.

var str = multiline(/*
<!doctype html>
<html>
    <body>
        <h1>❤ unicorns</h1>
    </body>
</html>
*/);
var str = 'foo\
bar';

This is not a multiline string. It's line-continuation. It doesn't preserve newlines, which is the main reason for wanting multiline strings.

You would need to do the following:

var str = 'foo\n\
bar';

But then you could just as well concatenate:

var str = 'foo\n' +
'bar';

Note that ES6 will have real multiline strings.

While it does work fine in the browser, it's mainly intended for use in Node.js. Use at your own risk.

$ npm install --save multiline

(with Browserify)

$ bower install --save multiline
  • Latest Chrome
  • Firefox >=17
  • Safari >=4
  • Opera >=9
  • Internet Explorer >=6

Even though minifiers strip comments by default there are ways to preserve them:

  • Uglify: Use /*@preserve instead of /* and enable the comments option
  • Closure Compiler: Use /*@preserve instead of /*
  • YUI Compressor: Use /*! instead of /*

You also need to add console.log after the comment so it's not removed as dead-code.

The final result would be:

var str = multiline(function(){/*!@preserve
<!doctype html>
<html>
    <body>
        <h1>❤ unicorns</h1>
    </body>
</html>
*/console.log});

MIT © Sindre Sorhus