gerhobbelt / theredoc

Makes your multi-line JavaScript strings look good

theredoc

A little template tag function that strips the leading indent from multi-line ES string templates. It also strips the first and last lines if they're just whitespace. If you're using template strings to write heredocs, you should try tagging them with theredoc to tidy them up a bit!

Install

$ npm install theredoc

Usage

const theredoc = require('theredoc')

function some () {
  function deeply () {
    function nested () {
      function code () {
        console.log(theredoc`
          I want to write multipline lines
          but don't want to mess up my indenting.
            Ok?
        `)
      }
    }
  }
}

Will look tidy in the code listing but output no superfluous indents:

I want to write multipline lines
but don't want to mess up my indenting.
  Ok?

Questions

Why should I use this?

Because good messages are often long messages, but out-of-the-box, ES template strings don't format multi-line error and console messages gracefully.

If you're familiar with """-style heredocs from CoffeeScript or the <<~-style heredoc from Ruby 2.3, you might appreciate being able to write multi-line strings with an indentation level that matches the surrounding code listing without indenting the resulting string itself.

For example, if you want to print a multi-line error message without superfluous indentation in the following situation, an unadorned template string would have to be outdented awkwardly:

        //...
      } catch (e) {
        console.error(`
Something bad happened.

  Message: ${e.message}
        `)
      }
      //...

Additionally, the newlines added to retain the formatting of the function call will be retained in the output, which you probably also don't want.

Instead, theredoc fixes both those issues by letting you write this:

        //...
      } catch (e) {
        console.error(theredoc`
          Something bad happened.

            Message: ${e.message}
        `)
      }
      //...

And the resulting console output will be:

Something bad happened.

  Message: LOL errors

With the leading 10 spaces stripped from each line and (since they only contain whitespace) having stripped the first and last lines of the template string.

If you still don't think this is nifty, I don't know what to tell you!

Why not use common-tags?

The very cool and fancy library common-tags can accomplish the same thing with the stripIndent function it exports, however there are a few downsides:

• It will trim all leading and trailing whitespace, which one might want to preserve
• It has a runtime dependency on babel-runtime, which drastically increases the size of its install and, because babel-runtime depends on core-js, sets a global object that might be more appropriate for an app to set than an intermediate lib
• While common-tags is really spiffy and you should check it out to learn about all the cool transforms you can do, 99.9% of the time I really just want indent-stripping heredocs

What about tabs (\t)?

Theredoc only deals with space character indentation, sorry!

A pull request to support tabs would be considered if (a) it didn't drastically increase the module's complexity, and (b) deferred to counting spaces in the event that the given string had some lines indented with spaces and other with \t tabs.