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Multiline strings in JavaScript

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Multiline strings in JavaScript

No more string concatenation or array join!

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

Before

var str = '' +
'<!doctype html>' +
'<html>' +
'	<body>' +
'		<h1>❤ unicorns</h1>' +
'	</body>' +
'</html>' +
'';

After

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

How

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.

Install

$ npm install --save multiline

Example

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>
*/});

console.log(str);

Which outputs:

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

And a real-world use-case.

Browser

Compatibility

  • Latest Chrome
  • Firefox >=17
  • Safari >=4
  • Opera >=9
  • Internet Explorer >=6

Minification

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 0 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>
*/0});

Install

Download manually or with a package-manager.

Bower

bower install --save multiline

Component

component install sindresorhus/multiline

Experiment

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>
*/);

FAQ

But JS already has multiline strings with \?

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.

License

MIT © Sindre Sorhus

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Multiline strings in JavaScript